a48d07afdf
Add direct migration support with fall back to swap. Direct migration support on top of the swap based page migration facility. This allows the direct migration of anonymous pages and the migration of file backed pages by dropping the associated buffers (requires writeout). Fall back to swap out if necessary. The patch is based on lots of patches from the hotplug project but the code was restructured, documented and simplified as much as possible. Note that an additional patch that defines the migrate_page() method for filesystems is necessary in order to avoid writeback for anonymous and file backed pages. Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Mike Kravetz <kravetz@us.ibm.com> Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
1897 lines
48 KiB
C
1897 lines
48 KiB
C
/*
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* linux/mm/vmscan.c
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*
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* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
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*
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* Swap reorganised 29.12.95, Stephen Tweedie.
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* kswapd added: 7.1.96 sct
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* Removed kswapd_ctl limits, and swap out as many pages as needed
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* to bring the system back to freepages.high: 2.4.97, Rik van Riel.
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* Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
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* Multiqueue VM started 5.8.00, Rik van Riel.
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*/
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#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/kernel_stat.h>
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#include <linux/swap.h>
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#include <linux/pagemap.h>
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#include <linux/init.h>
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#include <linux/highmem.h>
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#include <linux/file.h>
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#include <linux/writeback.h>
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#include <linux/blkdev.h>
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#include <linux/buffer_head.h> /* for try_to_release_page(),
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buffer_heads_over_limit */
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#include <linux/mm_inline.h>
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#include <linux/pagevec.h>
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#include <linux/backing-dev.h>
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#include <linux/rmap.h>
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#include <linux/topology.h>
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#include <linux/cpu.h>
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#include <linux/cpuset.h>
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#include <linux/notifier.h>
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#include <linux/rwsem.h>
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#include <asm/tlbflush.h>
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#include <asm/div64.h>
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#include <linux/swapops.h>
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/* possible outcome of pageout() */
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typedef enum {
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/* failed to write page out, page is locked */
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PAGE_KEEP,
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/* move page to the active list, page is locked */
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PAGE_ACTIVATE,
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/* page has been sent to the disk successfully, page is unlocked */
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PAGE_SUCCESS,
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/* page is clean and locked */
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PAGE_CLEAN,
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} pageout_t;
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struct scan_control {
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/* Ask refill_inactive_zone, or shrink_cache to scan this many pages */
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unsigned long nr_to_scan;
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/* Incremented by the number of inactive pages that were scanned */
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unsigned long nr_scanned;
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/* Incremented by the number of pages reclaimed */
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unsigned long nr_reclaimed;
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unsigned long nr_mapped; /* From page_state */
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/* Ask shrink_caches, or shrink_zone to scan at this priority */
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unsigned int priority;
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/* This context's GFP mask */
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gfp_t gfp_mask;
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int may_writepage;
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/* Can pages be swapped as part of reclaim? */
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int may_swap;
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/* This context's SWAP_CLUSTER_MAX. If freeing memory for
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* suspend, we effectively ignore SWAP_CLUSTER_MAX.
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* In this context, it doesn't matter that we scan the
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* whole list at once. */
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int swap_cluster_max;
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};
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/*
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* The list of shrinker callbacks used by to apply pressure to
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* ageable caches.
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*/
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struct shrinker {
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shrinker_t shrinker;
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struct list_head list;
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int seeks; /* seeks to recreate an obj */
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long nr; /* objs pending delete */
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};
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#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
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#ifdef ARCH_HAS_PREFETCH
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#define prefetch_prev_lru_page(_page, _base, _field) \
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do { \
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if ((_page)->lru.prev != _base) { \
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struct page *prev; \
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\
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prev = lru_to_page(&(_page->lru)); \
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prefetch(&prev->_field); \
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} \
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} while (0)
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#else
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#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
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#endif
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#ifdef ARCH_HAS_PREFETCHW
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#define prefetchw_prev_lru_page(_page, _base, _field) \
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do { \
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if ((_page)->lru.prev != _base) { \
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struct page *prev; \
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\
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prev = lru_to_page(&(_page->lru)); \
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prefetchw(&prev->_field); \
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} \
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} while (0)
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#else
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#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
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#endif
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/*
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* From 0 .. 100. Higher means more swappy.
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*/
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int vm_swappiness = 60;
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static long total_memory;
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static LIST_HEAD(shrinker_list);
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static DECLARE_RWSEM(shrinker_rwsem);
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/*
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* Add a shrinker callback to be called from the vm
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*/
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struct shrinker *set_shrinker(int seeks, shrinker_t theshrinker)
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{
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struct shrinker *shrinker;
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shrinker = kmalloc(sizeof(*shrinker), GFP_KERNEL);
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if (shrinker) {
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shrinker->shrinker = theshrinker;
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shrinker->seeks = seeks;
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shrinker->nr = 0;
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down_write(&shrinker_rwsem);
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list_add_tail(&shrinker->list, &shrinker_list);
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up_write(&shrinker_rwsem);
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}
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return shrinker;
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}
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EXPORT_SYMBOL(set_shrinker);
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/*
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* Remove one
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*/
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void remove_shrinker(struct shrinker *shrinker)
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{
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down_write(&shrinker_rwsem);
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list_del(&shrinker->list);
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up_write(&shrinker_rwsem);
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kfree(shrinker);
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}
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EXPORT_SYMBOL(remove_shrinker);
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#define SHRINK_BATCH 128
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/*
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* Call the shrink functions to age shrinkable caches
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*
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* Here we assume it costs one seek to replace a lru page and that it also
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* takes a seek to recreate a cache object. With this in mind we age equal
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* percentages of the lru and ageable caches. This should balance the seeks
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* generated by these structures.
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*
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* If the vm encounted mapped pages on the LRU it increase the pressure on
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* slab to avoid swapping.
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*
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* We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
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*
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* `lru_pages' represents the number of on-LRU pages in all the zones which
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* are eligible for the caller's allocation attempt. It is used for balancing
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* slab reclaim versus page reclaim.
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*
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* Returns the number of slab objects which we shrunk.
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*/
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int shrink_slab(unsigned long scanned, gfp_t gfp_mask, unsigned long lru_pages)
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{
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struct shrinker *shrinker;
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int ret = 0;
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if (scanned == 0)
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scanned = SWAP_CLUSTER_MAX;
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if (!down_read_trylock(&shrinker_rwsem))
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return 1; /* Assume we'll be able to shrink next time */
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list_for_each_entry(shrinker, &shrinker_list, list) {
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unsigned long long delta;
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unsigned long total_scan;
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unsigned long max_pass = (*shrinker->shrinker)(0, gfp_mask);
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delta = (4 * scanned) / shrinker->seeks;
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delta *= max_pass;
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do_div(delta, lru_pages + 1);
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shrinker->nr += delta;
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if (shrinker->nr < 0) {
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printk(KERN_ERR "%s: nr=%ld\n",
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__FUNCTION__, shrinker->nr);
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shrinker->nr = max_pass;
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}
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/*
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* Avoid risking looping forever due to too large nr value:
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* never try to free more than twice the estimate number of
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* freeable entries.
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*/
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if (shrinker->nr > max_pass * 2)
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shrinker->nr = max_pass * 2;
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total_scan = shrinker->nr;
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shrinker->nr = 0;
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while (total_scan >= SHRINK_BATCH) {
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long this_scan = SHRINK_BATCH;
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int shrink_ret;
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int nr_before;
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nr_before = (*shrinker->shrinker)(0, gfp_mask);
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shrink_ret = (*shrinker->shrinker)(this_scan, gfp_mask);
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if (shrink_ret == -1)
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break;
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if (shrink_ret < nr_before)
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ret += nr_before - shrink_ret;
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mod_page_state(slabs_scanned, this_scan);
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total_scan -= this_scan;
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cond_resched();
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}
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shrinker->nr += total_scan;
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}
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up_read(&shrinker_rwsem);
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return ret;
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}
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/* Called without lock on whether page is mapped, so answer is unstable */
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static inline int page_mapping_inuse(struct page *page)
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{
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struct address_space *mapping;
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/* Page is in somebody's page tables. */
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if (page_mapped(page))
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return 1;
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/* Be more reluctant to reclaim swapcache than pagecache */
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if (PageSwapCache(page))
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return 1;
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mapping = page_mapping(page);
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if (!mapping)
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return 0;
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/* File is mmap'd by somebody? */
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return mapping_mapped(mapping);
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}
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static inline int is_page_cache_freeable(struct page *page)
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{
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return page_count(page) - !!PagePrivate(page) == 2;
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}
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static int may_write_to_queue(struct backing_dev_info *bdi)
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{
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if (current->flags & PF_SWAPWRITE)
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return 1;
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if (!bdi_write_congested(bdi))
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return 1;
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if (bdi == current->backing_dev_info)
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return 1;
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return 0;
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}
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/*
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* We detected a synchronous write error writing a page out. Probably
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* -ENOSPC. We need to propagate that into the address_space for a subsequent
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* fsync(), msync() or close().
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*
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* The tricky part is that after writepage we cannot touch the mapping: nothing
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* prevents it from being freed up. But we have a ref on the page and once
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* that page is locked, the mapping is pinned.
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*
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* We're allowed to run sleeping lock_page() here because we know the caller has
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* __GFP_FS.
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*/
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static void handle_write_error(struct address_space *mapping,
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struct page *page, int error)
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{
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lock_page(page);
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if (page_mapping(page) == mapping) {
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if (error == -ENOSPC)
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set_bit(AS_ENOSPC, &mapping->flags);
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else
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set_bit(AS_EIO, &mapping->flags);
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}
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unlock_page(page);
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}
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/*
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* pageout is called by shrink_list() for each dirty page. Calls ->writepage().
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*/
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static pageout_t pageout(struct page *page, struct address_space *mapping)
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{
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/*
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* If the page is dirty, only perform writeback if that write
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* will be non-blocking. To prevent this allocation from being
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* stalled by pagecache activity. But note that there may be
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* stalls if we need to run get_block(). We could test
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* PagePrivate for that.
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*
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* If this process is currently in generic_file_write() against
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* this page's queue, we can perform writeback even if that
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* will block.
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*
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* If the page is swapcache, write it back even if that would
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* block, for some throttling. This happens by accident, because
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* swap_backing_dev_info is bust: it doesn't reflect the
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* congestion state of the swapdevs. Easy to fix, if needed.
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* See swapfile.c:page_queue_congested().
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*/
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if (!is_page_cache_freeable(page))
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return PAGE_KEEP;
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if (!mapping) {
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/*
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* Some data journaling orphaned pages can have
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* page->mapping == NULL while being dirty with clean buffers.
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*/
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if (PagePrivate(page)) {
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if (try_to_free_buffers(page)) {
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ClearPageDirty(page);
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printk("%s: orphaned page\n", __FUNCTION__);
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return PAGE_CLEAN;
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}
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}
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return PAGE_KEEP;
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}
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if (mapping->a_ops->writepage == NULL)
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return PAGE_ACTIVATE;
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if (!may_write_to_queue(mapping->backing_dev_info))
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return PAGE_KEEP;
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|
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if (clear_page_dirty_for_io(page)) {
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int res;
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struct writeback_control wbc = {
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.sync_mode = WB_SYNC_NONE,
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.nr_to_write = SWAP_CLUSTER_MAX,
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.nonblocking = 1,
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.for_reclaim = 1,
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};
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SetPageReclaim(page);
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res = mapping->a_ops->writepage(page, &wbc);
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if (res < 0)
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handle_write_error(mapping, page, res);
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if (res == AOP_WRITEPAGE_ACTIVATE) {
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ClearPageReclaim(page);
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return PAGE_ACTIVATE;
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}
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if (!PageWriteback(page)) {
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/* synchronous write or broken a_ops? */
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ClearPageReclaim(page);
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}
|
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return PAGE_SUCCESS;
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}
|
|
|
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return PAGE_CLEAN;
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}
|
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|
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static int remove_mapping(struct address_space *mapping, struct page *page)
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{
|
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if (!mapping)
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return 0; /* truncate got there first */
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|
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write_lock_irq(&mapping->tree_lock);
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|
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/*
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* The non-racy check for busy page. It is critical to check
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* PageDirty _after_ making sure that the page is freeable and
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* not in use by anybody. (pagecache + us == 2)
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*/
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if (unlikely(page_count(page) != 2))
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goto cannot_free;
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smp_rmb();
|
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if (unlikely(PageDirty(page)))
|
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goto cannot_free;
|
|
|
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if (PageSwapCache(page)) {
|
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swp_entry_t swap = { .val = page_private(page) };
|
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__delete_from_swap_cache(page);
|
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write_unlock_irq(&mapping->tree_lock);
|
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swap_free(swap);
|
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__put_page(page); /* The pagecache ref */
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return 1;
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}
|
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|
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__remove_from_page_cache(page);
|
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write_unlock_irq(&mapping->tree_lock);
|
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__put_page(page);
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return 1;
|
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|
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cannot_free:
|
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write_unlock_irq(&mapping->tree_lock);
|
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return 0;
|
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}
|
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|
|
/*
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* shrink_list adds the number of reclaimed pages to sc->nr_reclaimed
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*/
|
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static int shrink_list(struct list_head *page_list, struct scan_control *sc)
|
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{
|
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LIST_HEAD(ret_pages);
|
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struct pagevec freed_pvec;
|
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int pgactivate = 0;
|
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int reclaimed = 0;
|
|
|
|
cond_resched();
|
|
|
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pagevec_init(&freed_pvec, 1);
|
|
while (!list_empty(page_list)) {
|
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struct address_space *mapping;
|
|
struct page *page;
|
|
int may_enter_fs;
|
|
int referenced;
|
|
|
|
cond_resched();
|
|
|
|
page = lru_to_page(page_list);
|
|
list_del(&page->lru);
|
|
|
|
if (TestSetPageLocked(page))
|
|
goto keep;
|
|
|
|
BUG_ON(PageActive(page));
|
|
|
|
sc->nr_scanned++;
|
|
/* Double the slab pressure for mapped and swapcache pages */
|
|
if (page_mapped(page) || PageSwapCache(page))
|
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sc->nr_scanned++;
|
|
|
|
if (PageWriteback(page))
|
|
goto keep_locked;
|
|
|
|
referenced = page_referenced(page, 1);
|
|
/* In active use or really unfreeable? Activate it. */
|
|
if (referenced && page_mapping_inuse(page))
|
|
goto activate_locked;
|
|
|
|
#ifdef CONFIG_SWAP
|
|
/*
|
|
* Anonymous process memory has backing store?
|
|
* Try to allocate it some swap space here.
|
|
*/
|
|
if (PageAnon(page) && !PageSwapCache(page)) {
|
|
if (!sc->may_swap)
|
|
goto keep_locked;
|
|
if (!add_to_swap(page, GFP_ATOMIC))
|
|
goto activate_locked;
|
|
}
|
|
#endif /* CONFIG_SWAP */
|
|
|
|
mapping = page_mapping(page);
|
|
may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
|
|
(PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
|
|
|
|
/*
|
|
* The page is mapped into the page tables of one or more
|
|
* processes. Try to unmap it here.
|
|
*/
|
|
if (page_mapped(page) && mapping) {
|
|
/*
|
|
* No unmapping if we do not swap
|
|
*/
|
|
if (!sc->may_swap)
|
|
goto keep_locked;
|
|
|
|
switch (try_to_unmap(page, 0)) {
|
|
case SWAP_FAIL:
|
|
goto activate_locked;
|
|
case SWAP_AGAIN:
|
|
goto keep_locked;
|
|
case SWAP_SUCCESS:
|
|
; /* try to free the page below */
|
|
}
|
|
}
|
|
|
|
if (PageDirty(page)) {
|
|
if (referenced)
|
|
goto keep_locked;
|
|
if (!may_enter_fs)
|
|
goto keep_locked;
|
|
if (!sc->may_writepage)
|
|
goto keep_locked;
|
|
|
|
/* Page is dirty, try to write it out here */
|
|
switch(pageout(page, mapping)) {
|
|
case PAGE_KEEP:
|
|
goto keep_locked;
|
|
case PAGE_ACTIVATE:
|
|
goto activate_locked;
|
|
case PAGE_SUCCESS:
|
|
if (PageWriteback(page) || PageDirty(page))
|
|
goto keep;
|
|
/*
|
|
* A synchronous write - probably a ramdisk. Go
|
|
* ahead and try to reclaim the page.
|
|
*/
|
|
if (TestSetPageLocked(page))
|
|
goto keep;
|
|
if (PageDirty(page) || PageWriteback(page))
|
|
goto keep_locked;
|
|
mapping = page_mapping(page);
|
|
case PAGE_CLEAN:
|
|
; /* try to free the page below */
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If the page has buffers, try to free the buffer mappings
|
|
* associated with this page. If we succeed we try to free
|
|
* the page as well.
|
|
*
|
|
* We do this even if the page is PageDirty().
|
|
* try_to_release_page() does not perform I/O, but it is
|
|
* possible for a page to have PageDirty set, but it is actually
|
|
* clean (all its buffers are clean). This happens if the
|
|
* buffers were written out directly, with submit_bh(). ext3
|
|
* will do this, as well as the blockdev mapping.
|
|
* try_to_release_page() will discover that cleanness and will
|
|
* drop the buffers and mark the page clean - it can be freed.
|
|
*
|
|
* Rarely, pages can have buffers and no ->mapping. These are
|
|
* the pages which were not successfully invalidated in
|
|
* truncate_complete_page(). We try to drop those buffers here
|
|
* and if that worked, and the page is no longer mapped into
|
|
* process address space (page_count == 1) it can be freed.
|
|
* Otherwise, leave the page on the LRU so it is swappable.
|
|
*/
|
|
if (PagePrivate(page)) {
|
|
if (!try_to_release_page(page, sc->gfp_mask))
|
|
goto activate_locked;
|
|
if (!mapping && page_count(page) == 1)
|
|
goto free_it;
|
|
}
|
|
|
|
if (!remove_mapping(mapping, page))
|
|
goto keep_locked;
|
|
|
|
free_it:
|
|
unlock_page(page);
|
|
reclaimed++;
|
|
if (!pagevec_add(&freed_pvec, page))
|
|
__pagevec_release_nonlru(&freed_pvec);
|
|
continue;
|
|
|
|
activate_locked:
|
|
SetPageActive(page);
|
|
pgactivate++;
|
|
keep_locked:
|
|
unlock_page(page);
|
|
keep:
|
|
list_add(&page->lru, &ret_pages);
|
|
BUG_ON(PageLRU(page));
|
|
}
|
|
list_splice(&ret_pages, page_list);
|
|
if (pagevec_count(&freed_pvec))
|
|
__pagevec_release_nonlru(&freed_pvec);
|
|
mod_page_state(pgactivate, pgactivate);
|
|
sc->nr_reclaimed += reclaimed;
|
|
return reclaimed;
|
|
}
|
|
|
|
#ifdef CONFIG_MIGRATION
|
|
static inline void move_to_lru(struct page *page)
|
|
{
|
|
list_del(&page->lru);
|
|
if (PageActive(page)) {
|
|
/*
|
|
* lru_cache_add_active checks that
|
|
* the PG_active bit is off.
|
|
*/
|
|
ClearPageActive(page);
|
|
lru_cache_add_active(page);
|
|
} else {
|
|
lru_cache_add(page);
|
|
}
|
|
put_page(page);
|
|
}
|
|
|
|
/*
|
|
* Add isolated pages on the list back to the LRU.
|
|
*
|
|
* returns the number of pages put back.
|
|
*/
|
|
int putback_lru_pages(struct list_head *l)
|
|
{
|
|
struct page *page;
|
|
struct page *page2;
|
|
int count = 0;
|
|
|
|
list_for_each_entry_safe(page, page2, l, lru) {
|
|
move_to_lru(page);
|
|
count++;
|
|
}
|
|
return count;
|
|
}
|
|
|
|
/*
|
|
* swapout a single page
|
|
* page is locked upon entry, unlocked on exit
|
|
*/
|
|
static int swap_page(struct page *page)
|
|
{
|
|
struct address_space *mapping = page_mapping(page);
|
|
|
|
if (page_mapped(page) && mapping)
|
|
if (try_to_unmap(page, 0) != SWAP_SUCCESS)
|
|
goto unlock_retry;
|
|
|
|
if (PageDirty(page)) {
|
|
/* Page is dirty, try to write it out here */
|
|
switch(pageout(page, mapping)) {
|
|
case PAGE_KEEP:
|
|
case PAGE_ACTIVATE:
|
|
goto unlock_retry;
|
|
|
|
case PAGE_SUCCESS:
|
|
goto retry;
|
|
|
|
case PAGE_CLEAN:
|
|
; /* try to free the page below */
|
|
}
|
|
}
|
|
|
|
if (PagePrivate(page)) {
|
|
if (!try_to_release_page(page, GFP_KERNEL) ||
|
|
(!mapping && page_count(page) == 1))
|
|
goto unlock_retry;
|
|
}
|
|
|
|
if (remove_mapping(mapping, page)) {
|
|
/* Success */
|
|
unlock_page(page);
|
|
return 0;
|
|
}
|
|
|
|
unlock_retry:
|
|
unlock_page(page);
|
|
|
|
retry:
|
|
return -EAGAIN;
|
|
}
|
|
|
|
/*
|
|
* Page migration was first developed in the context of the memory hotplug
|
|
* project. The main authors of the migration code are:
|
|
*
|
|
* IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
|
|
* Hirokazu Takahashi <taka@valinux.co.jp>
|
|
* Dave Hansen <haveblue@us.ibm.com>
|
|
* Christoph Lameter <clameter@sgi.com>
|
|
*/
|
|
|
|
/*
|
|
* Remove references for a page and establish the new page with the correct
|
|
* basic settings to be able to stop accesses to the page.
|
|
*/
|
|
static int migrate_page_remove_references(struct page *newpage,
|
|
struct page *page, int nr_refs)
|
|
{
|
|
struct address_space *mapping = page_mapping(page);
|
|
struct page **radix_pointer;
|
|
|
|
/*
|
|
* Avoid doing any of the following work if the page count
|
|
* indicates that the page is in use or truncate has removed
|
|
* the page.
|
|
*/
|
|
if (!mapping || page_mapcount(page) + nr_refs != page_count(page))
|
|
return 1;
|
|
|
|
/*
|
|
* Establish swap ptes for anonymous pages or destroy pte
|
|
* maps for files.
|
|
*
|
|
* In order to reestablish file backed mappings the fault handlers
|
|
* will take the radix tree_lock which may then be used to stop
|
|
* processses from accessing this page until the new page is ready.
|
|
*
|
|
* A process accessing via a swap pte (an anonymous page) will take a
|
|
* page_lock on the old page which will block the process until the
|
|
* migration attempt is complete. At that time the PageSwapCache bit
|
|
* will be examined. If the page was migrated then the PageSwapCache
|
|
* bit will be clear and the operation to retrieve the page will be
|
|
* retried which will find the new page in the radix tree. Then a new
|
|
* direct mapping may be generated based on the radix tree contents.
|
|
*
|
|
* If the page was not migrated then the PageSwapCache bit
|
|
* is still set and the operation may continue.
|
|
*/
|
|
try_to_unmap(page, 1);
|
|
|
|
/*
|
|
* Give up if we were unable to remove all mappings.
|
|
*/
|
|
if (page_mapcount(page))
|
|
return 1;
|
|
|
|
write_lock_irq(&mapping->tree_lock);
|
|
|
|
radix_pointer = (struct page **)radix_tree_lookup_slot(
|
|
&mapping->page_tree,
|
|
page_index(page));
|
|
|
|
if (!page_mapping(page) || page_count(page) != nr_refs ||
|
|
*radix_pointer != page) {
|
|
write_unlock_irq(&mapping->tree_lock);
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* Now we know that no one else is looking at the page.
|
|
*
|
|
* Certain minimal information about a page must be available
|
|
* in order for other subsystems to properly handle the page if they
|
|
* find it through the radix tree update before we are finished
|
|
* copying the page.
|
|
*/
|
|
get_page(newpage);
|
|
newpage->index = page->index;
|
|
newpage->mapping = page->mapping;
|
|
if (PageSwapCache(page)) {
|
|
SetPageSwapCache(newpage);
|
|
set_page_private(newpage, page_private(page));
|
|
}
|
|
|
|
*radix_pointer = newpage;
|
|
__put_page(page);
|
|
write_unlock_irq(&mapping->tree_lock);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Copy the page to its new location
|
|
*/
|
|
void migrate_page_copy(struct page *newpage, struct page *page)
|
|
{
|
|
copy_highpage(newpage, page);
|
|
|
|
if (PageError(page))
|
|
SetPageError(newpage);
|
|
if (PageReferenced(page))
|
|
SetPageReferenced(newpage);
|
|
if (PageUptodate(page))
|
|
SetPageUptodate(newpage);
|
|
if (PageActive(page))
|
|
SetPageActive(newpage);
|
|
if (PageChecked(page))
|
|
SetPageChecked(newpage);
|
|
if (PageMappedToDisk(page))
|
|
SetPageMappedToDisk(newpage);
|
|
|
|
if (PageDirty(page)) {
|
|
clear_page_dirty_for_io(page);
|
|
set_page_dirty(newpage);
|
|
}
|
|
|
|
ClearPageSwapCache(page);
|
|
ClearPageActive(page);
|
|
ClearPagePrivate(page);
|
|
set_page_private(page, 0);
|
|
page->mapping = NULL;
|
|
|
|
/*
|
|
* If any waiters have accumulated on the new page then
|
|
* wake them up.
|
|
*/
|
|
if (PageWriteback(newpage))
|
|
end_page_writeback(newpage);
|
|
}
|
|
|
|
/*
|
|
* Common logic to directly migrate a single page suitable for
|
|
* pages that do not use PagePrivate.
|
|
*
|
|
* Pages are locked upon entry and exit.
|
|
*/
|
|
int migrate_page(struct page *newpage, struct page *page)
|
|
{
|
|
BUG_ON(PageWriteback(page)); /* Writeback must be complete */
|
|
|
|
if (migrate_page_remove_references(newpage, page, 2))
|
|
return -EAGAIN;
|
|
|
|
migrate_page_copy(newpage, page);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* migrate_pages
|
|
*
|
|
* Two lists are passed to this function. The first list
|
|
* contains the pages isolated from the LRU to be migrated.
|
|
* The second list contains new pages that the pages isolated
|
|
* can be moved to. If the second list is NULL then all
|
|
* pages are swapped out.
|
|
*
|
|
* The function returns after 10 attempts or if no pages
|
|
* are movable anymore because t has become empty
|
|
* or no retryable pages exist anymore.
|
|
*
|
|
* Return: Number of pages not migrated when "to" ran empty.
|
|
*/
|
|
int migrate_pages(struct list_head *from, struct list_head *to,
|
|
struct list_head *moved, struct list_head *failed)
|
|
{
|
|
int retry;
|
|
int nr_failed = 0;
|
|
int pass = 0;
|
|
struct page *page;
|
|
struct page *page2;
|
|
int swapwrite = current->flags & PF_SWAPWRITE;
|
|
int rc;
|
|
|
|
if (!swapwrite)
|
|
current->flags |= PF_SWAPWRITE;
|
|
|
|
redo:
|
|
retry = 0;
|
|
|
|
list_for_each_entry_safe(page, page2, from, lru) {
|
|
struct page *newpage = NULL;
|
|
struct address_space *mapping;
|
|
|
|
cond_resched();
|
|
|
|
rc = 0;
|
|
if (page_count(page) == 1)
|
|
/* page was freed from under us. So we are done. */
|
|
goto next;
|
|
|
|
if (to && list_empty(to))
|
|
break;
|
|
|
|
/*
|
|
* Skip locked pages during the first two passes to give the
|
|
* functions holding the lock time to release the page. Later we
|
|
* use lock_page() to have a higher chance of acquiring the
|
|
* lock.
|
|
*/
|
|
rc = -EAGAIN;
|
|
if (pass > 2)
|
|
lock_page(page);
|
|
else
|
|
if (TestSetPageLocked(page))
|
|
goto next;
|
|
|
|
/*
|
|
* Only wait on writeback if we have already done a pass where
|
|
* we we may have triggered writeouts for lots of pages.
|
|
*/
|
|
if (pass > 0) {
|
|
wait_on_page_writeback(page);
|
|
} else {
|
|
if (PageWriteback(page))
|
|
goto unlock_page;
|
|
}
|
|
|
|
/*
|
|
* Anonymous pages must have swap cache references otherwise
|
|
* the information contained in the page maps cannot be
|
|
* preserved.
|
|
*/
|
|
if (PageAnon(page) && !PageSwapCache(page)) {
|
|
if (!add_to_swap(page, GFP_KERNEL)) {
|
|
rc = -ENOMEM;
|
|
goto unlock_page;
|
|
}
|
|
}
|
|
|
|
if (!to) {
|
|
rc = swap_page(page);
|
|
goto next;
|
|
}
|
|
|
|
newpage = lru_to_page(to);
|
|
lock_page(newpage);
|
|
|
|
/*
|
|
* Pages are properly locked and writeback is complete.
|
|
* Try to migrate the page.
|
|
*/
|
|
mapping = page_mapping(page);
|
|
if (!mapping)
|
|
goto unlock_both;
|
|
|
|
/*
|
|
* Trigger writeout if page is dirty
|
|
*/
|
|
if (PageDirty(page)) {
|
|
switch (pageout(page, mapping)) {
|
|
case PAGE_KEEP:
|
|
case PAGE_ACTIVATE:
|
|
goto unlock_both;
|
|
|
|
case PAGE_SUCCESS:
|
|
unlock_page(newpage);
|
|
goto next;
|
|
|
|
case PAGE_CLEAN:
|
|
; /* try to migrate the page below */
|
|
}
|
|
}
|
|
/*
|
|
* If we have no buffer or can release the buffer
|
|
* then do a simple migration.
|
|
*/
|
|
if (!page_has_buffers(page) ||
|
|
try_to_release_page(page, GFP_KERNEL)) {
|
|
rc = migrate_page(newpage, page);
|
|
goto unlock_both;
|
|
}
|
|
|
|
/*
|
|
* On early passes with mapped pages simply
|
|
* retry. There may be a lock held for some
|
|
* buffers that may go away. Later
|
|
* swap them out.
|
|
*/
|
|
if (pass > 4) {
|
|
unlock_page(newpage);
|
|
newpage = NULL;
|
|
rc = swap_page(page);
|
|
goto next;
|
|
}
|
|
|
|
unlock_both:
|
|
unlock_page(newpage);
|
|
|
|
unlock_page:
|
|
unlock_page(page);
|
|
|
|
next:
|
|
if (rc == -EAGAIN) {
|
|
retry++;
|
|
} else if (rc) {
|
|
/* Permanent failure */
|
|
list_move(&page->lru, failed);
|
|
nr_failed++;
|
|
} else {
|
|
if (newpage) {
|
|
/* Successful migration. Return page to LRU */
|
|
move_to_lru(newpage);
|
|
}
|
|
list_move(&page->lru, moved);
|
|
}
|
|
}
|
|
if (retry && pass++ < 10)
|
|
goto redo;
|
|
|
|
if (!swapwrite)
|
|
current->flags &= ~PF_SWAPWRITE;
|
|
|
|
return nr_failed + retry;
|
|
}
|
|
|
|
/*
|
|
* Isolate one page from the LRU lists and put it on the
|
|
* indicated list with elevated refcount.
|
|
*
|
|
* Result:
|
|
* 0 = page not on LRU list
|
|
* 1 = page removed from LRU list and added to the specified list.
|
|
*/
|
|
int isolate_lru_page(struct page *page)
|
|
{
|
|
int ret = 0;
|
|
|
|
if (PageLRU(page)) {
|
|
struct zone *zone = page_zone(page);
|
|
spin_lock_irq(&zone->lru_lock);
|
|
if (TestClearPageLRU(page)) {
|
|
ret = 1;
|
|
get_page(page);
|
|
if (PageActive(page))
|
|
del_page_from_active_list(zone, page);
|
|
else
|
|
del_page_from_inactive_list(zone, page);
|
|
}
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* zone->lru_lock is heavily contended. Some of the functions that
|
|
* shrink the lists perform better by taking out a batch of pages
|
|
* and working on them outside the LRU lock.
|
|
*
|
|
* For pagecache intensive workloads, this function is the hottest
|
|
* spot in the kernel (apart from copy_*_user functions).
|
|
*
|
|
* Appropriate locks must be held before calling this function.
|
|
*
|
|
* @nr_to_scan: The number of pages to look through on the list.
|
|
* @src: The LRU list to pull pages off.
|
|
* @dst: The temp list to put pages on to.
|
|
* @scanned: The number of pages that were scanned.
|
|
*
|
|
* returns how many pages were moved onto *@dst.
|
|
*/
|
|
static int isolate_lru_pages(int nr_to_scan, struct list_head *src,
|
|
struct list_head *dst, int *scanned)
|
|
{
|
|
int nr_taken = 0;
|
|
struct page *page;
|
|
int scan = 0;
|
|
|
|
while (scan++ < nr_to_scan && !list_empty(src)) {
|
|
page = lru_to_page(src);
|
|
prefetchw_prev_lru_page(page, src, flags);
|
|
|
|
if (!TestClearPageLRU(page))
|
|
BUG();
|
|
list_del(&page->lru);
|
|
if (get_page_testone(page)) {
|
|
/*
|
|
* It is being freed elsewhere
|
|
*/
|
|
__put_page(page);
|
|
SetPageLRU(page);
|
|
list_add(&page->lru, src);
|
|
continue;
|
|
} else {
|
|
list_add(&page->lru, dst);
|
|
nr_taken++;
|
|
}
|
|
}
|
|
|
|
*scanned = scan;
|
|
return nr_taken;
|
|
}
|
|
|
|
/*
|
|
* shrink_cache() adds the number of pages reclaimed to sc->nr_reclaimed
|
|
*/
|
|
static void shrink_cache(struct zone *zone, struct scan_control *sc)
|
|
{
|
|
LIST_HEAD(page_list);
|
|
struct pagevec pvec;
|
|
int max_scan = sc->nr_to_scan;
|
|
|
|
pagevec_init(&pvec, 1);
|
|
|
|
lru_add_drain();
|
|
spin_lock_irq(&zone->lru_lock);
|
|
while (max_scan > 0) {
|
|
struct page *page;
|
|
int nr_taken;
|
|
int nr_scan;
|
|
int nr_freed;
|
|
|
|
nr_taken = isolate_lru_pages(sc->swap_cluster_max,
|
|
&zone->inactive_list,
|
|
&page_list, &nr_scan);
|
|
zone->nr_inactive -= nr_taken;
|
|
zone->pages_scanned += nr_scan;
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
|
|
if (nr_taken == 0)
|
|
goto done;
|
|
|
|
max_scan -= nr_scan;
|
|
nr_freed = shrink_list(&page_list, sc);
|
|
|
|
local_irq_disable();
|
|
if (current_is_kswapd()) {
|
|
__mod_page_state_zone(zone, pgscan_kswapd, nr_scan);
|
|
__mod_page_state(kswapd_steal, nr_freed);
|
|
} else
|
|
__mod_page_state_zone(zone, pgscan_direct, nr_scan);
|
|
__mod_page_state_zone(zone, pgsteal, nr_freed);
|
|
|
|
spin_lock(&zone->lru_lock);
|
|
/*
|
|
* Put back any unfreeable pages.
|
|
*/
|
|
while (!list_empty(&page_list)) {
|
|
page = lru_to_page(&page_list);
|
|
if (TestSetPageLRU(page))
|
|
BUG();
|
|
list_del(&page->lru);
|
|
if (PageActive(page))
|
|
add_page_to_active_list(zone, page);
|
|
else
|
|
add_page_to_inactive_list(zone, page);
|
|
if (!pagevec_add(&pvec, page)) {
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
__pagevec_release(&pvec);
|
|
spin_lock_irq(&zone->lru_lock);
|
|
}
|
|
}
|
|
}
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
done:
|
|
pagevec_release(&pvec);
|
|
}
|
|
|
|
/*
|
|
* This moves pages from the active list to the inactive list.
|
|
*
|
|
* We move them the other way if the page is referenced by one or more
|
|
* processes, from rmap.
|
|
*
|
|
* If the pages are mostly unmapped, the processing is fast and it is
|
|
* appropriate to hold zone->lru_lock across the whole operation. But if
|
|
* the pages are mapped, the processing is slow (page_referenced()) so we
|
|
* should drop zone->lru_lock around each page. It's impossible to balance
|
|
* this, so instead we remove the pages from the LRU while processing them.
|
|
* It is safe to rely on PG_active against the non-LRU pages in here because
|
|
* nobody will play with that bit on a non-LRU page.
|
|
*
|
|
* The downside is that we have to touch page->_count against each page.
|
|
* But we had to alter page->flags anyway.
|
|
*/
|
|
static void
|
|
refill_inactive_zone(struct zone *zone, struct scan_control *sc)
|
|
{
|
|
int pgmoved;
|
|
int pgdeactivate = 0;
|
|
int pgscanned;
|
|
int nr_pages = sc->nr_to_scan;
|
|
LIST_HEAD(l_hold); /* The pages which were snipped off */
|
|
LIST_HEAD(l_inactive); /* Pages to go onto the inactive_list */
|
|
LIST_HEAD(l_active); /* Pages to go onto the active_list */
|
|
struct page *page;
|
|
struct pagevec pvec;
|
|
int reclaim_mapped = 0;
|
|
long mapped_ratio;
|
|
long distress;
|
|
long swap_tendency;
|
|
|
|
lru_add_drain();
|
|
spin_lock_irq(&zone->lru_lock);
|
|
pgmoved = isolate_lru_pages(nr_pages, &zone->active_list,
|
|
&l_hold, &pgscanned);
|
|
zone->pages_scanned += pgscanned;
|
|
zone->nr_active -= pgmoved;
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
|
|
/*
|
|
* `distress' is a measure of how much trouble we're having reclaiming
|
|
* pages. 0 -> no problems. 100 -> great trouble.
|
|
*/
|
|
distress = 100 >> zone->prev_priority;
|
|
|
|
/*
|
|
* The point of this algorithm is to decide when to start reclaiming
|
|
* mapped memory instead of just pagecache. Work out how much memory
|
|
* is mapped.
|
|
*/
|
|
mapped_ratio = (sc->nr_mapped * 100) / total_memory;
|
|
|
|
/*
|
|
* Now decide how much we really want to unmap some pages. The mapped
|
|
* ratio is downgraded - just because there's a lot of mapped memory
|
|
* doesn't necessarily mean that page reclaim isn't succeeding.
|
|
*
|
|
* The distress ratio is important - we don't want to start going oom.
|
|
*
|
|
* A 100% value of vm_swappiness overrides this algorithm altogether.
|
|
*/
|
|
swap_tendency = mapped_ratio / 2 + distress + vm_swappiness;
|
|
|
|
/*
|
|
* Now use this metric to decide whether to start moving mapped memory
|
|
* onto the inactive list.
|
|
*/
|
|
if (swap_tendency >= 100)
|
|
reclaim_mapped = 1;
|
|
|
|
while (!list_empty(&l_hold)) {
|
|
cond_resched();
|
|
page = lru_to_page(&l_hold);
|
|
list_del(&page->lru);
|
|
if (page_mapped(page)) {
|
|
if (!reclaim_mapped ||
|
|
(total_swap_pages == 0 && PageAnon(page)) ||
|
|
page_referenced(page, 0)) {
|
|
list_add(&page->lru, &l_active);
|
|
continue;
|
|
}
|
|
}
|
|
list_add(&page->lru, &l_inactive);
|
|
}
|
|
|
|
pagevec_init(&pvec, 1);
|
|
pgmoved = 0;
|
|
spin_lock_irq(&zone->lru_lock);
|
|
while (!list_empty(&l_inactive)) {
|
|
page = lru_to_page(&l_inactive);
|
|
prefetchw_prev_lru_page(page, &l_inactive, flags);
|
|
if (TestSetPageLRU(page))
|
|
BUG();
|
|
if (!TestClearPageActive(page))
|
|
BUG();
|
|
list_move(&page->lru, &zone->inactive_list);
|
|
pgmoved++;
|
|
if (!pagevec_add(&pvec, page)) {
|
|
zone->nr_inactive += pgmoved;
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
pgdeactivate += pgmoved;
|
|
pgmoved = 0;
|
|
if (buffer_heads_over_limit)
|
|
pagevec_strip(&pvec);
|
|
__pagevec_release(&pvec);
|
|
spin_lock_irq(&zone->lru_lock);
|
|
}
|
|
}
|
|
zone->nr_inactive += pgmoved;
|
|
pgdeactivate += pgmoved;
|
|
if (buffer_heads_over_limit) {
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
pagevec_strip(&pvec);
|
|
spin_lock_irq(&zone->lru_lock);
|
|
}
|
|
|
|
pgmoved = 0;
|
|
while (!list_empty(&l_active)) {
|
|
page = lru_to_page(&l_active);
|
|
prefetchw_prev_lru_page(page, &l_active, flags);
|
|
if (TestSetPageLRU(page))
|
|
BUG();
|
|
BUG_ON(!PageActive(page));
|
|
list_move(&page->lru, &zone->active_list);
|
|
pgmoved++;
|
|
if (!pagevec_add(&pvec, page)) {
|
|
zone->nr_active += pgmoved;
|
|
pgmoved = 0;
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
__pagevec_release(&pvec);
|
|
spin_lock_irq(&zone->lru_lock);
|
|
}
|
|
}
|
|
zone->nr_active += pgmoved;
|
|
spin_unlock(&zone->lru_lock);
|
|
|
|
__mod_page_state_zone(zone, pgrefill, pgscanned);
|
|
__mod_page_state(pgdeactivate, pgdeactivate);
|
|
local_irq_enable();
|
|
|
|
pagevec_release(&pvec);
|
|
}
|
|
|
|
/*
|
|
* This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
|
|
*/
|
|
static void
|
|
shrink_zone(struct zone *zone, struct scan_control *sc)
|
|
{
|
|
unsigned long nr_active;
|
|
unsigned long nr_inactive;
|
|
|
|
atomic_inc(&zone->reclaim_in_progress);
|
|
|
|
/*
|
|
* Add one to `nr_to_scan' just to make sure that the kernel will
|
|
* slowly sift through the active list.
|
|
*/
|
|
zone->nr_scan_active += (zone->nr_active >> sc->priority) + 1;
|
|
nr_active = zone->nr_scan_active;
|
|
if (nr_active >= sc->swap_cluster_max)
|
|
zone->nr_scan_active = 0;
|
|
else
|
|
nr_active = 0;
|
|
|
|
zone->nr_scan_inactive += (zone->nr_inactive >> sc->priority) + 1;
|
|
nr_inactive = zone->nr_scan_inactive;
|
|
if (nr_inactive >= sc->swap_cluster_max)
|
|
zone->nr_scan_inactive = 0;
|
|
else
|
|
nr_inactive = 0;
|
|
|
|
while (nr_active || nr_inactive) {
|
|
if (nr_active) {
|
|
sc->nr_to_scan = min(nr_active,
|
|
(unsigned long)sc->swap_cluster_max);
|
|
nr_active -= sc->nr_to_scan;
|
|
refill_inactive_zone(zone, sc);
|
|
}
|
|
|
|
if (nr_inactive) {
|
|
sc->nr_to_scan = min(nr_inactive,
|
|
(unsigned long)sc->swap_cluster_max);
|
|
nr_inactive -= sc->nr_to_scan;
|
|
shrink_cache(zone, sc);
|
|
}
|
|
}
|
|
|
|
throttle_vm_writeout();
|
|
|
|
atomic_dec(&zone->reclaim_in_progress);
|
|
}
|
|
|
|
/*
|
|
* This is the direct reclaim path, for page-allocating processes. We only
|
|
* try to reclaim pages from zones which will satisfy the caller's allocation
|
|
* request.
|
|
*
|
|
* We reclaim from a zone even if that zone is over pages_high. Because:
|
|
* a) The caller may be trying to free *extra* pages to satisfy a higher-order
|
|
* allocation or
|
|
* b) The zones may be over pages_high but they must go *over* pages_high to
|
|
* satisfy the `incremental min' zone defense algorithm.
|
|
*
|
|
* Returns the number of reclaimed pages.
|
|
*
|
|
* If a zone is deemed to be full of pinned pages then just give it a light
|
|
* scan then give up on it.
|
|
*/
|
|
static void
|
|
shrink_caches(struct zone **zones, struct scan_control *sc)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; zones[i] != NULL; i++) {
|
|
struct zone *zone = zones[i];
|
|
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
|
|
continue;
|
|
|
|
zone->temp_priority = sc->priority;
|
|
if (zone->prev_priority > sc->priority)
|
|
zone->prev_priority = sc->priority;
|
|
|
|
if (zone->all_unreclaimable && sc->priority != DEF_PRIORITY)
|
|
continue; /* Let kswapd poll it */
|
|
|
|
shrink_zone(zone, sc);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* This is the main entry point to direct page reclaim.
|
|
*
|
|
* If a full scan of the inactive list fails to free enough memory then we
|
|
* are "out of memory" and something needs to be killed.
|
|
*
|
|
* If the caller is !__GFP_FS then the probability of a failure is reasonably
|
|
* high - the zone may be full of dirty or under-writeback pages, which this
|
|
* caller can't do much about. We kick pdflush and take explicit naps in the
|
|
* hope that some of these pages can be written. But if the allocating task
|
|
* holds filesystem locks which prevent writeout this might not work, and the
|
|
* allocation attempt will fail.
|
|
*/
|
|
int try_to_free_pages(struct zone **zones, gfp_t gfp_mask)
|
|
{
|
|
int priority;
|
|
int ret = 0;
|
|
int total_scanned = 0, total_reclaimed = 0;
|
|
struct reclaim_state *reclaim_state = current->reclaim_state;
|
|
struct scan_control sc;
|
|
unsigned long lru_pages = 0;
|
|
int i;
|
|
|
|
sc.gfp_mask = gfp_mask;
|
|
sc.may_writepage = !laptop_mode;
|
|
sc.may_swap = 1;
|
|
|
|
inc_page_state(allocstall);
|
|
|
|
for (i = 0; zones[i] != NULL; i++) {
|
|
struct zone *zone = zones[i];
|
|
|
|
if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
|
|
continue;
|
|
|
|
zone->temp_priority = DEF_PRIORITY;
|
|
lru_pages += zone->nr_active + zone->nr_inactive;
|
|
}
|
|
|
|
for (priority = DEF_PRIORITY; priority >= 0; priority--) {
|
|
sc.nr_mapped = read_page_state(nr_mapped);
|
|
sc.nr_scanned = 0;
|
|
sc.nr_reclaimed = 0;
|
|
sc.priority = priority;
|
|
sc.swap_cluster_max = SWAP_CLUSTER_MAX;
|
|
if (!priority)
|
|
disable_swap_token();
|
|
shrink_caches(zones, &sc);
|
|
shrink_slab(sc.nr_scanned, gfp_mask, lru_pages);
|
|
if (reclaim_state) {
|
|
sc.nr_reclaimed += reclaim_state->reclaimed_slab;
|
|
reclaim_state->reclaimed_slab = 0;
|
|
}
|
|
total_scanned += sc.nr_scanned;
|
|
total_reclaimed += sc.nr_reclaimed;
|
|
if (total_reclaimed >= sc.swap_cluster_max) {
|
|
ret = 1;
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* Try to write back as many pages as we just scanned. This
|
|
* tends to cause slow streaming writers to write data to the
|
|
* disk smoothly, at the dirtying rate, which is nice. But
|
|
* that's undesirable in laptop mode, where we *want* lumpy
|
|
* writeout. So in laptop mode, write out the whole world.
|
|
*/
|
|
if (total_scanned > sc.swap_cluster_max + sc.swap_cluster_max/2) {
|
|
wakeup_pdflush(laptop_mode ? 0 : total_scanned);
|
|
sc.may_writepage = 1;
|
|
}
|
|
|
|
/* Take a nap, wait for some writeback to complete */
|
|
if (sc.nr_scanned && priority < DEF_PRIORITY - 2)
|
|
blk_congestion_wait(WRITE, HZ/10);
|
|
}
|
|
out:
|
|
for (i = 0; zones[i] != 0; i++) {
|
|
struct zone *zone = zones[i];
|
|
|
|
if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
|
|
continue;
|
|
|
|
zone->prev_priority = zone->temp_priority;
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* For kswapd, balance_pgdat() will work across all this node's zones until
|
|
* they are all at pages_high.
|
|
*
|
|
* If `nr_pages' is non-zero then it is the number of pages which are to be
|
|
* reclaimed, regardless of the zone occupancies. This is a software suspend
|
|
* special.
|
|
*
|
|
* Returns the number of pages which were actually freed.
|
|
*
|
|
* There is special handling here for zones which are full of pinned pages.
|
|
* This can happen if the pages are all mlocked, or if they are all used by
|
|
* device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
|
|
* What we do is to detect the case where all pages in the zone have been
|
|
* scanned twice and there has been zero successful reclaim. Mark the zone as
|
|
* dead and from now on, only perform a short scan. Basically we're polling
|
|
* the zone for when the problem goes away.
|
|
*
|
|
* kswapd scans the zones in the highmem->normal->dma direction. It skips
|
|
* zones which have free_pages > pages_high, but once a zone is found to have
|
|
* free_pages <= pages_high, we scan that zone and the lower zones regardless
|
|
* of the number of free pages in the lower zones. This interoperates with
|
|
* the page allocator fallback scheme to ensure that aging of pages is balanced
|
|
* across the zones.
|
|
*/
|
|
static int balance_pgdat(pg_data_t *pgdat, int nr_pages, int order)
|
|
{
|
|
int to_free = nr_pages;
|
|
int all_zones_ok;
|
|
int priority;
|
|
int i;
|
|
int total_scanned, total_reclaimed;
|
|
struct reclaim_state *reclaim_state = current->reclaim_state;
|
|
struct scan_control sc;
|
|
|
|
loop_again:
|
|
total_scanned = 0;
|
|
total_reclaimed = 0;
|
|
sc.gfp_mask = GFP_KERNEL;
|
|
sc.may_writepage = !laptop_mode;
|
|
sc.may_swap = 1;
|
|
sc.nr_mapped = read_page_state(nr_mapped);
|
|
|
|
inc_page_state(pageoutrun);
|
|
|
|
for (i = 0; i < pgdat->nr_zones; i++) {
|
|
struct zone *zone = pgdat->node_zones + i;
|
|
|
|
zone->temp_priority = DEF_PRIORITY;
|
|
}
|
|
|
|
for (priority = DEF_PRIORITY; priority >= 0; priority--) {
|
|
int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
|
|
unsigned long lru_pages = 0;
|
|
|
|
/* The swap token gets in the way of swapout... */
|
|
if (!priority)
|
|
disable_swap_token();
|
|
|
|
all_zones_ok = 1;
|
|
|
|
if (nr_pages == 0) {
|
|
/*
|
|
* Scan in the highmem->dma direction for the highest
|
|
* zone which needs scanning
|
|
*/
|
|
for (i = pgdat->nr_zones - 1; i >= 0; i--) {
|
|
struct zone *zone = pgdat->node_zones + i;
|
|
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
if (zone->all_unreclaimable &&
|
|
priority != DEF_PRIORITY)
|
|
continue;
|
|
|
|
if (!zone_watermark_ok(zone, order,
|
|
zone->pages_high, 0, 0)) {
|
|
end_zone = i;
|
|
goto scan;
|
|
}
|
|
}
|
|
goto out;
|
|
} else {
|
|
end_zone = pgdat->nr_zones - 1;
|
|
}
|
|
scan:
|
|
for (i = 0; i <= end_zone; i++) {
|
|
struct zone *zone = pgdat->node_zones + i;
|
|
|
|
lru_pages += zone->nr_active + zone->nr_inactive;
|
|
}
|
|
|
|
/*
|
|
* Now scan the zone in the dma->highmem direction, stopping
|
|
* at the last zone which needs scanning.
|
|
*
|
|
* We do this because the page allocator works in the opposite
|
|
* direction. This prevents the page allocator from allocating
|
|
* pages behind kswapd's direction of progress, which would
|
|
* cause too much scanning of the lower zones.
|
|
*/
|
|
for (i = 0; i <= end_zone; i++) {
|
|
struct zone *zone = pgdat->node_zones + i;
|
|
int nr_slab;
|
|
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
if (zone->all_unreclaimable && priority != DEF_PRIORITY)
|
|
continue;
|
|
|
|
if (nr_pages == 0) { /* Not software suspend */
|
|
if (!zone_watermark_ok(zone, order,
|
|
zone->pages_high, end_zone, 0))
|
|
all_zones_ok = 0;
|
|
}
|
|
zone->temp_priority = priority;
|
|
if (zone->prev_priority > priority)
|
|
zone->prev_priority = priority;
|
|
sc.nr_scanned = 0;
|
|
sc.nr_reclaimed = 0;
|
|
sc.priority = priority;
|
|
sc.swap_cluster_max = nr_pages? nr_pages : SWAP_CLUSTER_MAX;
|
|
atomic_inc(&zone->reclaim_in_progress);
|
|
shrink_zone(zone, &sc);
|
|
atomic_dec(&zone->reclaim_in_progress);
|
|
reclaim_state->reclaimed_slab = 0;
|
|
nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
|
|
lru_pages);
|
|
sc.nr_reclaimed += reclaim_state->reclaimed_slab;
|
|
total_reclaimed += sc.nr_reclaimed;
|
|
total_scanned += sc.nr_scanned;
|
|
if (zone->all_unreclaimable)
|
|
continue;
|
|
if (nr_slab == 0 && zone->pages_scanned >=
|
|
(zone->nr_active + zone->nr_inactive) * 4)
|
|
zone->all_unreclaimable = 1;
|
|
/*
|
|
* If we've done a decent amount of scanning and
|
|
* the reclaim ratio is low, start doing writepage
|
|
* even in laptop mode
|
|
*/
|
|
if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
|
|
total_scanned > total_reclaimed+total_reclaimed/2)
|
|
sc.may_writepage = 1;
|
|
}
|
|
if (nr_pages && to_free > total_reclaimed)
|
|
continue; /* swsusp: need to do more work */
|
|
if (all_zones_ok)
|
|
break; /* kswapd: all done */
|
|
/*
|
|
* OK, kswapd is getting into trouble. Take a nap, then take
|
|
* another pass across the zones.
|
|
*/
|
|
if (total_scanned && priority < DEF_PRIORITY - 2)
|
|
blk_congestion_wait(WRITE, HZ/10);
|
|
|
|
/*
|
|
* We do this so kswapd doesn't build up large priorities for
|
|
* example when it is freeing in parallel with allocators. It
|
|
* matches the direct reclaim path behaviour in terms of impact
|
|
* on zone->*_priority.
|
|
*/
|
|
if ((total_reclaimed >= SWAP_CLUSTER_MAX) && (!nr_pages))
|
|
break;
|
|
}
|
|
out:
|
|
for (i = 0; i < pgdat->nr_zones; i++) {
|
|
struct zone *zone = pgdat->node_zones + i;
|
|
|
|
zone->prev_priority = zone->temp_priority;
|
|
}
|
|
if (!all_zones_ok) {
|
|
cond_resched();
|
|
goto loop_again;
|
|
}
|
|
|
|
return total_reclaimed;
|
|
}
|
|
|
|
/*
|
|
* The background pageout daemon, started as a kernel thread
|
|
* from the init process.
|
|
*
|
|
* This basically trickles out pages so that we have _some_
|
|
* free memory available even if there is no other activity
|
|
* that frees anything up. This is needed for things like routing
|
|
* etc, where we otherwise might have all activity going on in
|
|
* asynchronous contexts that cannot page things out.
|
|
*
|
|
* If there are applications that are active memory-allocators
|
|
* (most normal use), this basically shouldn't matter.
|
|
*/
|
|
static int kswapd(void *p)
|
|
{
|
|
unsigned long order;
|
|
pg_data_t *pgdat = (pg_data_t*)p;
|
|
struct task_struct *tsk = current;
|
|
DEFINE_WAIT(wait);
|
|
struct reclaim_state reclaim_state = {
|
|
.reclaimed_slab = 0,
|
|
};
|
|
cpumask_t cpumask;
|
|
|
|
daemonize("kswapd%d", pgdat->node_id);
|
|
cpumask = node_to_cpumask(pgdat->node_id);
|
|
if (!cpus_empty(cpumask))
|
|
set_cpus_allowed(tsk, cpumask);
|
|
current->reclaim_state = &reclaim_state;
|
|
|
|
/*
|
|
* Tell the memory management that we're a "memory allocator",
|
|
* and that if we need more memory we should get access to it
|
|
* regardless (see "__alloc_pages()"). "kswapd" should
|
|
* never get caught in the normal page freeing logic.
|
|
*
|
|
* (Kswapd normally doesn't need memory anyway, but sometimes
|
|
* you need a small amount of memory in order to be able to
|
|
* page out something else, and this flag essentially protects
|
|
* us from recursively trying to free more memory as we're
|
|
* trying to free the first piece of memory in the first place).
|
|
*/
|
|
tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
|
|
|
|
order = 0;
|
|
for ( ; ; ) {
|
|
unsigned long new_order;
|
|
|
|
try_to_freeze();
|
|
|
|
prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
|
|
new_order = pgdat->kswapd_max_order;
|
|
pgdat->kswapd_max_order = 0;
|
|
if (order < new_order) {
|
|
/*
|
|
* Don't sleep if someone wants a larger 'order'
|
|
* allocation
|
|
*/
|
|
order = new_order;
|
|
} else {
|
|
schedule();
|
|
order = pgdat->kswapd_max_order;
|
|
}
|
|
finish_wait(&pgdat->kswapd_wait, &wait);
|
|
|
|
balance_pgdat(pgdat, 0, order);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* A zone is low on free memory, so wake its kswapd task to service it.
|
|
*/
|
|
void wakeup_kswapd(struct zone *zone, int order)
|
|
{
|
|
pg_data_t *pgdat;
|
|
|
|
if (!populated_zone(zone))
|
|
return;
|
|
|
|
pgdat = zone->zone_pgdat;
|
|
if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
|
|
return;
|
|
if (pgdat->kswapd_max_order < order)
|
|
pgdat->kswapd_max_order = order;
|
|
if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
|
|
return;
|
|
if (!waitqueue_active(&pgdat->kswapd_wait))
|
|
return;
|
|
wake_up_interruptible(&pgdat->kswapd_wait);
|
|
}
|
|
|
|
#ifdef CONFIG_PM
|
|
/*
|
|
* Try to free `nr_pages' of memory, system-wide. Returns the number of freed
|
|
* pages.
|
|
*/
|
|
int shrink_all_memory(int nr_pages)
|
|
{
|
|
pg_data_t *pgdat;
|
|
int nr_to_free = nr_pages;
|
|
int ret = 0;
|
|
struct reclaim_state reclaim_state = {
|
|
.reclaimed_slab = 0,
|
|
};
|
|
|
|
current->reclaim_state = &reclaim_state;
|
|
for_each_pgdat(pgdat) {
|
|
int freed;
|
|
freed = balance_pgdat(pgdat, nr_to_free, 0);
|
|
ret += freed;
|
|
nr_to_free -= freed;
|
|
if (nr_to_free <= 0)
|
|
break;
|
|
}
|
|
current->reclaim_state = NULL;
|
|
return ret;
|
|
}
|
|
#endif
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
/* It's optimal to keep kswapds on the same CPUs as their memory, but
|
|
not required for correctness. So if the last cpu in a node goes
|
|
away, we get changed to run anywhere: as the first one comes back,
|
|
restore their cpu bindings. */
|
|
static int __devinit cpu_callback(struct notifier_block *nfb,
|
|
unsigned long action,
|
|
void *hcpu)
|
|
{
|
|
pg_data_t *pgdat;
|
|
cpumask_t mask;
|
|
|
|
if (action == CPU_ONLINE) {
|
|
for_each_pgdat(pgdat) {
|
|
mask = node_to_cpumask(pgdat->node_id);
|
|
if (any_online_cpu(mask) != NR_CPUS)
|
|
/* One of our CPUs online: restore mask */
|
|
set_cpus_allowed(pgdat->kswapd, mask);
|
|
}
|
|
}
|
|
return NOTIFY_OK;
|
|
}
|
|
#endif /* CONFIG_HOTPLUG_CPU */
|
|
|
|
static int __init kswapd_init(void)
|
|
{
|
|
pg_data_t *pgdat;
|
|
swap_setup();
|
|
for_each_pgdat(pgdat)
|
|
pgdat->kswapd
|
|
= find_task_by_pid(kernel_thread(kswapd, pgdat, CLONE_KERNEL));
|
|
total_memory = nr_free_pagecache_pages();
|
|
hotcpu_notifier(cpu_callback, 0);
|
|
return 0;
|
|
}
|
|
|
|
module_init(kswapd_init)
|
|
|
|
#ifdef CONFIG_NUMA
|
|
/*
|
|
* Zone reclaim mode
|
|
*
|
|
* If non-zero call zone_reclaim when the number of free pages falls below
|
|
* the watermarks.
|
|
*
|
|
* In the future we may add flags to the mode. However, the page allocator
|
|
* should only have to check that zone_reclaim_mode != 0 before calling
|
|
* zone_reclaim().
|
|
*/
|
|
int zone_reclaim_mode __read_mostly;
|
|
|
|
#define RECLAIM_OFF 0
|
|
#define RECLAIM_ZONE (1<<0) /* Run shrink_cache on the zone */
|
|
#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
|
|
#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
|
|
#define RECLAIM_SLAB (1<<3) /* Do a global slab shrink if the zone is out of memory */
|
|
|
|
/*
|
|
* Mininum time between zone reclaim scans
|
|
*/
|
|
int zone_reclaim_interval __read_mostly = 30*HZ;
|
|
|
|
/*
|
|
* Priority for ZONE_RECLAIM. This determines the fraction of pages
|
|
* of a node considered for each zone_reclaim. 4 scans 1/16th of
|
|
* a zone.
|
|
*/
|
|
#define ZONE_RECLAIM_PRIORITY 4
|
|
|
|
/*
|
|
* Try to free up some pages from this zone through reclaim.
|
|
*/
|
|
int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
|
|
{
|
|
int nr_pages;
|
|
struct task_struct *p = current;
|
|
struct reclaim_state reclaim_state;
|
|
struct scan_control sc;
|
|
cpumask_t mask;
|
|
int node_id;
|
|
|
|
if (time_before(jiffies,
|
|
zone->last_unsuccessful_zone_reclaim + zone_reclaim_interval))
|
|
return 0;
|
|
|
|
if (!(gfp_mask & __GFP_WAIT) ||
|
|
zone->all_unreclaimable ||
|
|
atomic_read(&zone->reclaim_in_progress) > 0)
|
|
return 0;
|
|
|
|
node_id = zone->zone_pgdat->node_id;
|
|
mask = node_to_cpumask(node_id);
|
|
if (!cpus_empty(mask) && node_id != numa_node_id())
|
|
return 0;
|
|
|
|
sc.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE);
|
|
sc.may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP);
|
|
sc.nr_scanned = 0;
|
|
sc.nr_reclaimed = 0;
|
|
sc.priority = ZONE_RECLAIM_PRIORITY + 1;
|
|
sc.nr_mapped = read_page_state(nr_mapped);
|
|
sc.gfp_mask = gfp_mask;
|
|
|
|
disable_swap_token();
|
|
|
|
nr_pages = 1 << order;
|
|
if (nr_pages > SWAP_CLUSTER_MAX)
|
|
sc.swap_cluster_max = nr_pages;
|
|
else
|
|
sc.swap_cluster_max = SWAP_CLUSTER_MAX;
|
|
|
|
cond_resched();
|
|
p->flags |= PF_MEMALLOC;
|
|
reclaim_state.reclaimed_slab = 0;
|
|
p->reclaim_state = &reclaim_state;
|
|
|
|
/*
|
|
* Free memory by calling shrink zone with increasing priorities
|
|
* until we have enough memory freed.
|
|
*/
|
|
do {
|
|
sc.priority--;
|
|
shrink_zone(zone, &sc);
|
|
|
|
} while (sc.nr_reclaimed < nr_pages && sc.priority > 0);
|
|
|
|
if (sc.nr_reclaimed < nr_pages && (zone_reclaim_mode & RECLAIM_SLAB)) {
|
|
/*
|
|
* shrink_slab does not currently allow us to determine
|
|
* how many pages were freed in the zone. So we just
|
|
* shake the slab and then go offnode for a single allocation.
|
|
*
|
|
* shrink_slab will free memory on all zones and may take
|
|
* a long time.
|
|
*/
|
|
shrink_slab(sc.nr_scanned, gfp_mask, order);
|
|
sc.nr_reclaimed = 1; /* Avoid getting the off node timeout */
|
|
}
|
|
|
|
p->reclaim_state = NULL;
|
|
current->flags &= ~PF_MEMALLOC;
|
|
|
|
if (sc.nr_reclaimed == 0)
|
|
zone->last_unsuccessful_zone_reclaim = jiffies;
|
|
|
|
return sc.nr_reclaimed >= nr_pages;
|
|
}
|
|
#endif
|
|
|