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mm/zsmalloc: use a proper page type

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Let's clean it up: use a proper page type and store our data (offset into
a page) in the lower 16 bit as documented.

We won't be able to support 256 KiB base pages, which is acceptable. 
Teach Kconfig to handle that cleanly using a new CONFIG_HAVE_ZSMALLOC.

Based on this, we should do a proper "struct zsdesc" conversion, as
proposed in [1].

This removes the last _mapcount/page_type offender.

[1] https://lore.kernel.org/all/20231130101242.2590384-1-42.hyeyoo@gmail.com/

Link: https://lkml.kernel.org/r/20240529111904.2069608-4-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Tested-by: Sergey Senozhatsky <senozhatsky@chromium.org>	[zram/zsmalloc workloads]
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2024-05-29 13:19:01 +02:00 committed by Andrew Morton
parent 8db00ad564
commit 43d746dc49
4 changed files with 37 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
drivers/block/zram/Kconfig
View File

@ -2,6 +2,7 @@
config ZRAM
tristate "Compressed RAM block device support"
depends on BLOCK && SYSFS && MMU
depends on HAVE_ZSMALLOC
depends on CRYPTO_LZO || CRYPTO_ZSTD || CRYPTO_LZ4 || CRYPTO_LZ4HC || CRYPTO_842
select ZSMALLOC
help

3
include/linux/page-flags.h
View File

@ -947,6 +947,7 @@ enum pagetype {
PG_guard = 0x08000000,
PG_hugetlb = 0x04000000,
PG_slab = 0x02000000,
PG_zsmalloc = 0x01000000,
PAGE_TYPE_BASE = 0x80000000,
@ -1071,6 +1072,8 @@ FOLIO_TYPE_OPS(hugetlb, hugetlb)
FOLIO_TEST_FLAG_FALSE(hugetlb)
#endif
PAGE_TYPE_OPS(Zsmalloc, zsmalloc, zsmalloc)
/**
* PageHuge - Determine if the page belongs to hugetlbfs
* @page: The page to test.

10
mm/Kconfig
View File

@ -128,7 +128,7 @@ config ZSWAP_COMPRESSOR_DEFAULT
choice
prompt "Default allocator"
depends on ZSWAP
default ZSWAP_ZPOOL_DEFAULT_ZSMALLOC if MMU
default ZSWAP_ZPOOL_DEFAULT_ZSMALLOC if HAVE_ZSMALLOC
default ZSWAP_ZPOOL_DEFAULT_ZBUD
help
Selects the default allocator for the compressed cache for
@ -154,6 +154,7 @@ config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
bool "zsmalloc"
depends on HAVE_ZSMALLOC
select ZSMALLOC
help
Use the zsmalloc allocator as the default allocator.
@ -186,10 +187,15 @@ config Z3FOLD
page. It is a ZBUD derivative so the simplicity and determinism are
still there.
config HAVE_ZSMALLOC
def_bool y
depends on MMU
depends on PAGE_SIZE_LESS_THAN_256KB # we want <= 64 KiB
config ZSMALLOC
tristate
prompt "N:1 compression allocator (zsmalloc)" if ZSWAP
depends on MMU
depends on HAVE_ZSMALLOC
help
zsmalloc is a slab-based memory allocator designed to store
pages of various compression levels efficiently. It achieves

29
mm/zsmalloc.c
View File

@ -20,7 +20,8 @@
* page->index: links together all component pages of a zspage
* For the huge page, this is always 0, so we use this field
* to store handle.
* page->page_type: first object offset in a subpage of zspage
* page->page_type: PG_zsmalloc, lower 16 bit locate the first object
* offset in a subpage of a zspage
*
* Usage of struct page flags:
* PG_private: identifies the first component page
@ -450,14 +451,28 @@ static inline struct page *get_first_page(struct zspage *zspage)
return first_page;
}
#define FIRST_OBJ_PAGE_TYPE_MASK 0xffff
static inline void reset_first_obj_offset(struct page *page)
{
VM_WARN_ON_ONCE(!PageZsmalloc(page));
page->page_type |= FIRST_OBJ_PAGE_TYPE_MASK;
}
static inline unsigned int get_first_obj_offset(struct page *page)
{
return page->page_type;
VM_WARN_ON_ONCE(!PageZsmalloc(page));
return page->page_type & FIRST_OBJ_PAGE_TYPE_MASK;
}
static inline void set_first_obj_offset(struct page *page, unsigned int offset)
{
page->page_type = offset;
/* With 16 bit available, we can support offsets into 64 KiB pages. */
BUILD_BUG_ON(PAGE_SIZE > SZ_64K);
VM_WARN_ON_ONCE(!PageZsmalloc(page));
VM_WARN_ON_ONCE(offset & ~FIRST_OBJ_PAGE_TYPE_MASK);
page->page_type &= ~FIRST_OBJ_PAGE_TYPE_MASK;
page->page_type |= offset & FIRST_OBJ_PAGE_TYPE_MASK;
}
static inline unsigned int get_freeobj(struct zspage *zspage)
@ -791,8 +806,9 @@ static void reset_page(struct page *page)
__ClearPageMovable(page);
ClearPagePrivate(page);
set_page_private(page, 0);
page_mapcount_reset(page);
page->index = 0;
reset_first_obj_offset(page);
__ClearPageZsmalloc(page);
}
static int trylock_zspage(struct zspage *zspage)
@ -965,11 +981,13 @@ static struct zspage *alloc_zspage(struct zs_pool *pool,
if (!page) {
while (--i >= 0) {
dec_zone_page_state(pages[i], NR_ZSPAGES);
__ClearPageZsmalloc(pages[i]);
__free_page(pages[i]);
}
cache_free_zspage(pool, zspage);
return NULL;
}
__SetPageZsmalloc(page);
inc_zone_page_state(page, NR_ZSPAGES);
pages[i] = page;
@ -1754,6 +1772,9 @@ static int zs_page_migrate(struct page *newpage, struct page *page,
VM_BUG_ON_PAGE(!PageIsolated(page), page);
/* We're committed, tell the world that this is a Zsmalloc page. */
__SetPageZsmalloc(newpage);
/* The page is locked, so this pointer must remain valid */
zspage = get_zspage(page);
pool = zspage->pool;