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There is no need to do anything if sysfs_slab_alias() return nonzero
value after getting a mergeable cache.
Signed-off-by: Xiongwei Song <xiongwei.song@windriver.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Link: https://lore.kernel.org/all/e5ebc952-af17-321f-5343-bc914d47c931@suse.cz/
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
As reported by coccicheck:
./mm/slab.c:3253:2-59: code aligned with following code on line 3255.
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Acked-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Acked-by: David Rientjes <rientjes@google.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Transhuge swapcaches won't be freed in __collapse_huge_page_copy(). It's
because release_pte_page() is not called for these pages and thus
free_page_and_swap_cache can't grab the page lock. These pages won't be
freed from swap cache even if we are the only user until next time
reclaim. It shouldn't hurt indeed, but we could try to free these pages
to save more memory for system.
Link: https://lkml.kernel.org/r/20220625092816.4856-8-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The return value of khugepaged_add_pte_mapped_thp() is always 0 and also
ignored. Remove it to clean up the code.
Link: https://lkml.kernel.org/r/20220625092816.4856-7-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Zach O'Keefe <zokeefe@google.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
nr_none is always 0 for non-shmem case because the page can be read from
the backend store. So when nr_none ! = 0, it must be in is_shmem case.
Also only adjust the nrpages and uncharge shmem when nr_none != 0 to save
cpu cycles.
Link: https://lkml.kernel.org/r/20220625092816.4856-5-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Zach O'Keefe <zokeefe@google.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Fix some typos and tweak the code to meet codestyle. No functional change
intended.
Link: https://lkml.kernel.org/r/20220625092816.4856-4-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Zach O'Keefe <zokeefe@google.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When do_swap_page returns VM_FAULT_RETRY, we do not retry here and thus
swap entry will remain in pagetable. This will result in later failure.
So stop swapping in pages in this case to save cpu cycles. As A further
optimization, mmap_lock is released when __collapse_huge_page_swapin()
fails to avoid relocking mmap_lock. And "swapped_in++" is moved after
error handling to make it more accurate.
Link: https://lkml.kernel.org/r/20220625092816.4856-3-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "A few cleanup patches for khugepaged", v2.
This series contains a few cleaup patches to remove unneeded return value,
use helper macro, fix typos and so on. More details can be found in the
respective changelogs.
This patch (of 7):
If we reach here, khugepaged_scan_mm_slot() has already made sure that
hugepage is enabled for shmem, via its call to hugepage_vma_check().
Remove this duplicated check.
Link: https://lkml.kernel.org/r/20220625092816.4856-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20220625092816.4856-2-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: Zach O'Keefe <zokeefe@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Howells <dhowells@redhat.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Commit e5251fd43007 ("mm/hugetlb: introduce set_huge_swap_pte_at()
helper") add set_huge_swap_pte_at() to handle swap entries on
architectures that support hugepages consisting of contiguous ptes. And
currently the set_huge_swap_pte_at() is only overridden by arm64.
set_huge_swap_pte_at() provide a sz parameter to help determine the number
of entries to be updated. But in fact, all hugetlb swap entries contain
pfn information, so we can find the corresponding folio through the pfn
recorded in the swap entry, then the folio_size() is the number of entries
that need to be updated.
And considering that users will easily cause bugs by ignoring the
difference between set_huge_swap_pte_at() and set_huge_pte_at(). Let's
handle swap entries in set_huge_pte_at() and remove the
set_huge_swap_pte_at(), then we can call set_huge_pte_at() anywhere, which
simplifies our coding.
Link: https://lkml.kernel.org/r/20220626145717.53572-1-zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Acked-by: Muchun Song <songmuchun@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Not all systems use swap, so estimating available memory would help to
prevent swapping or OOM of system that not use swap.
And we need to reserve some page cache to prevent swapping or thrashing.
If somebody is accessing the pages in pagecache, and if too much would be
freed, most accesses might mean reading data from disk, i.e. thrashing.
Link: https://lkml.kernel.org/r/20220623020833.972979-1-yang.yang29@zte.com.cn
Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
Signed-off-by: CGEL ZTE <cgel.zte@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Comments that mention mem_hotplug_end() are confusing as there is no
function called mem_hotplug_end(). Fix them by replacing all the
occurences of mem_hotplug_end() in the comments with mem_hotplug_done().
[akpm@linux-foundation.org: grammatical fixes]
Link: https://lkml.kernel.org/r/20220620071516.1286101-1-p76091292@gs.ncku.edu.tw
Signed-off-by: Yun-Ze Li <p76091292@gs.ncku.edu.tw>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Passing index to pte_offset_map_lock() directly so the below calculation
can be avoided. Rename orig_pte to ptep as it's not changed. Also use
helper is_swap_pte() to improve the readability. No functional change
intended.
[akpm@linux-foundation.org: reduce scope of `ptep']
Link: https://lkml.kernel.org/r/20220618090527.37843-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
commit 641844f5616d ("mm/hugetlb: introduce minimum hugepage order") fixed
a static checker warning and introduced a global variable minimum_order to
fix the warning. However, the local variable in
dissolve_free_huge_pages() can be initialized to
huge_page_order(&default_hstate) to fix the warning.
So remove minimum_order to simplify the code.
Link: https://lkml.kernel.org/r/20220616033846.96937-1-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
For now, the feature of hugetlb_free_vmemmap is not compatible with the
feature of memory_hotplug.memmap_on_memory, and hugetlb_free_vmemmap takes
precedence over memory_hotplug.memmap_on_memory. However, someone wants
to make memory_hotplug.memmap_on_memory takes precedence over
hugetlb_free_vmemmap since memmap_on_memory makes it more likely to
succeed memory hotplug in close-to-OOM situations. So the decision of
making hugetlb_free_vmemmap take precedence is not wise and elegant.
The proper approach is to have hugetlb_vmemmap.c do the check whether the
section which the HugeTLB pages belong to can be optimized. If the
section's vmemmap pages are allocated from the added memory block itself,
hugetlb_free_vmemmap should refuse to optimize the vmemmap, otherwise, do
the optimization. Then both kernel parameters are compatible. So this
patch introduces VmemmapSelfHosted to mask any non-optimizable vmemmap
pages. The hugetlb_vmemmap can use this flag to detect if a vmemmap page
can be optimized.
[songmuchun@bytedance.com: walk vmemmap page tables to avoid false-positive]
Link: https://lkml.kernel.org/r/20220620110616.12056-3-songmuchun@bytedance.com
Link: https://lkml.kernel.org/r/20220617135650.74901-3-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Co-developed-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "make hugetlb_optimize_vmemmap compatible with
memmap_on_memory", v3.
This series makes hugetlb_optimize_vmemmap compatible with
memmap_on_memory.
This patch (of 2):
We are almost running out of section flags, only one bit is available in
the worst case (powerpc with 256k pages). However, there are still some
free bits (in ->section_mem_map) on other architectures (e.g. x86_64 has
10 bits available, arm64 has 8 bits available with worst case of 64K
pages). We have hard coded those numbers in code, it is inconvenient to
use those bits on other architectures except powerpc. So transfer those
section flags to enumeration to make it easy to add new section flags in
the future. Also, move SECTION_TAINT_ZONE_DEVICE into the scope of
CONFIG_ZONE_DEVICE to save a bit on non-zone-device case.
[songmuchun@bytedance.com: replace enum with defines per David]
Link: https://lkml.kernel.org/r/20220620110616.12056-2-songmuchun@bytedance.com
Link: https://lkml.kernel.org/r/20220617135650.74901-1-songmuchun@bytedance.com
Link: https://lkml.kernel.org/r/20220617135650.74901-2-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The only caller already has a folio, so push the folio->page conversion
down a level.
Link: https://lkml.kernel.org/r/20220617175020.717127-21-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
All callers now have a folio, so push the folio->page conversion
down to this function.
[akpm@linux-foundation.org: uninline destroy_large_folio() to fix build issue]
Link: https://lkml.kernel.org/r/20220617175020.717127-20-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
All the callers now have a folio. Saves several calls to compound_head,
totalling 502 bytes of text.
Link: https://lkml.kernel.org/r/20220617175020.717127-19-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
All the callers now have a folio, so pass it in. This doesn't
save any text, but it does save a call to compound_head() as
folio_test_hugetlb() does not contain a call like PageHuge() does.
Link: https://lkml.kernel.org/r/20220617175020.717127-18-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Pages linked through the LRU list cannot be tail pages as ->compound_head
is in a union with one of the words of the list_head, and they cannot
be ZONE_DEVICE pages as ->pgmap is in a union with the same word.
Saves 60 bytes of text by removing a call to page_is_fake_head().
Link: https://lkml.kernel.org/r/20220617175020.717127-15-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This function was already calling compound_head(), but now it can
cache the result of calling compound_head() and avoid calling it again.
Saves 299 bytes of text by avoiding various calls to compound_page()
and avoiding checks of PageTail.
Link: https://lkml.kernel.org/r/20220617175020.717127-14-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Save a few calls to compound_head by converting the passed page to
a folio. Reduces kernel text size by 74 bytes.
Link: https://lkml.kernel.org/r/20220617175020.717127-13-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Do the per-cpu dereferencing of the fbatches once which saves 14 bytes
of text and several percpu relocations.
Link: https://lkml.kernel.org/r/20220617175020.717127-12-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The function is too long, so pull this complicated conditional out into
cpu_needs_drain(). This ends up shrinking the text by 14 bytes,
by allowing GCC to cache the result of calling per_cpu() instead of
relocating each lookup individually.
Link: https://lkml.kernel.org/r/20220617175020.717127-11-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
No change to generated code, but this struct no longer contains any
pagevecs, and not all the folio batches it contains are lru.
Link: https://lkml.kernel.org/r/20220617175020.717127-10-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Rename it to just 'activate', saving 696 bytes of text from removals
of compound_page() and the pagevec_lru_move_fn() infrastructure.
Inline need_activate_page_drain() into its only caller.
Link: https://lkml.kernel.org/r/20220617175020.717127-9-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Using folios instead of pages removes several calls to compound_head(),
shrinking the kernel by 1089 bytes of text.
Link: https://lkml.kernel.org/r/20220617175020.717127-8-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Using folios instead of pages shrinks deactivate_page() and
lru_deactivate_fn() by 778 bytes between them.
Link: https://lkml.kernel.org/r/20220617175020.717127-7-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Use a folio throughout lru_deactivate_file_fn(), removing many hidden
calls to compound_head(). Shrinks the kernel by 864 bytes of text.
Link: https://lkml.kernel.org/r/20220617175020.717127-6-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When adding folios to the LRU for the first time, the LRU flag will
already be clear, so skip the test-and-clear part of moving from one
LRU to another.
Removes 285 bytes from kernel text, mostly due to removing
__pagevec_lru_add().
Link: https://lkml.kernel.org/r/20220617175020.717127-5-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
__pagevec_lru_add has no callers outside swap.c, so make it static,
and move it to a more logical position in the file.
Link: https://lkml.kernel.org/r/20220617175020.717127-4-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Start converting the LRU from pagevecs to folio_batches.
Combine the functionality of pagevec_add_and_need_flush() with
pagevec_lru_move_fn() in the new folio_batch_add_and_move().
Convert the lru_rotate pagevec to a folio_batch.
Adds 223 bytes total to kernel text, because we're duplicating
infrastructure. This will be more than made up for in future patches.
Link: https://lkml.kernel.org/r/20220617175020.717127-3-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Remove a few hidden calls to compound_head, saving 76 bytes of text.
Link: https://lkml.kernel.org/r/20220617154248.700416-6-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Remove a few hidden calls to compound_head, saving 411 bytes of text.
Link: https://lkml.kernel.org/r/20220617154248.700416-5-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Remove a few hidden calls to compound_head, saving 387 bytes of text on
my test configuration.
Link: https://lkml.kernel.org/r/20220617154248.700416-4-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Remove a few hidden calls to compound_head, saving 279 bytes of text.
Link: https://lkml.kernel.org/r/20220617154248.700416-3-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "nvert much of vmscan to folios"
vmscan always operates on folios since it puts the pages on the LRU list.
Switching all of these functions from pages to folios saves 1483 bytes of
text from removing all the baggage around calling compound_page() and
similar functions.
This patch (of 5):
This is a straightforward conversion which removes several hidden calls
to compound_head, saving 330 bytes of kernel text.
Link: https://lkml.kernel.org/r/20220617154248.700416-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20220617154248.700416-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Similar to our MM_CP_DIRTY_ACCT handling for shared, writable mappings, we
can try mapping anonymous pages in a private writable mapping writable if
they are exclusive, the PTE is already dirty, and no special handling
applies. Mapping the anonymous page writable is essentially the same
thing the write fault handler would do in this case.
Special handling is required for uffd-wp and softdirty tracking, so take
care of that properly. Also, leave PROT_NONE handling alone for now; in
the future, we could similarly extend the logic in do_numa_page() or use
pte_mk_savedwrite() here.
While this improves mprotect(PROT_READ)+mprotect(PROT_READ|PROT_WRITE)
performance, it should also be a valuable optimization for uffd-wp, when
un-protecting.
This has been previously suggested by Peter Collingbourne in [1], relevant
in the context of the Scudo memory allocator, before we had
PageAnonExclusive.
This commit doesn't add the same handling for PMDs (i.e., anonymous THP,
anonymous hugetlb); benchmark results from Andrea indicate that there are
minor performance gains, so it's might still be valuable to streamline
that logic for all anonymous pages in the future.
As we now also set MM_CP_DIRTY_ACCT for private mappings, let's rename it
to MM_CP_TRY_CHANGE_WRITABLE, to make it clearer what's actually
happening.
Micro-benchmark courtesy of Andrea:
===
#define _GNU_SOURCE
#include <sys/mman.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#define SIZE (1024*1024*1024)
int main(int argc, char *argv[])
{
char *p;
if (posix_memalign((void **)&p, sysconf(_SC_PAGESIZE)*512, SIZE))
perror("posix_memalign"), exit(1);
if (madvise(p, SIZE, argc > 1 ? MADV_HUGEPAGE : MADV_NOHUGEPAGE))
perror("madvise");
explicit_bzero(p, SIZE);
for (int loops = 0; loops < 40; loops++) {
if (mprotect(p, SIZE, PROT_READ))
perror("mprotect"), exit(1);
if (mprotect(p, SIZE, PROT_READ|PROT_WRITE))
perror("mprotect"), exit(1);
explicit_bzero(p, SIZE);
}
}
===
Results on my Ryzen 9 3900X:
Stock 10 runs (lower is better): AVG 6.398s, STDEV 0.043
Patched 10 runs (lower is better): AVG 3.780s, STDEV 0.026
===
[1] https://lkml.kernel.org/r/20210429214801.2583336-1-pcc@google.com
Link: https://lkml.kernel.org/r/20220614093629.76309-1-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Suggested-by: Peter Collingbourne <pcc@google.com>
Acked-by: Peter Xu <peterx@redhat.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Users can do data access-aware LRU-lists sorting using 'LRU_PRIO' and
'LRU_DEPRIO' DAMOS actions. However, finding best parameters including
the hotness/coldness thresholds, CPU quota, and watermarks could be
challenging for some users. To make the scheme easy to be used without
complex tuning for common situations, this commit implements a static
kernel module called 'DAMON_LRU_SORT' using the 'LRU_PRIO' and
'LRU_DEPRIO' DAMOS actions.
It proactively sorts LRU-lists using DAMON with conservatively chosen
default values of the parameters. That is, the module under its default
parameters will make no harm for common situations but provide some level
of efficiency improvements for systems having clear hot/cold access
pattern under a level of memory pressure while consuming only a limited
small portion of CPU time.
Link: https://lkml.kernel.org/r/20220613192301.8817-9-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit adds a new DAMON-based operation scheme action called
'LRU_DEPRIO' for physical address space. The action deprioritizes pages
in the memory area of the target access pattern on their LRU lists. This
is hence supposed to be used for rarely accessed (cold) memory regions so
that cold pages could be more likely reclaimed first under memory
pressure. Internally, it simply calls 'lru_deactivate()'.
Using this with 'LRU_PRIO' action for hot pages, users can proactively
sort LRU lists based on the access pattern. That is, it can make the LRU
lists somewhat more trustworthy source of access temperature. As a
result, efficiency of LRU-lists based mechanisms including the reclamation
target selection could be improved.
Link: https://lkml.kernel.org/r/20220613192301.8817-7-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit adds a new DAMOS action called 'LRU_PRIO' for the physical
address space. The action prioritizes pages in the memory regions of the
user-specified target access pattern on their LRU lists. This is hence
supposed to be used for frequently accessed (hot) memory regions so that
hot pages could be more likely protected under memory pressure.
Internally, it simply calls 'mark_page_accessed()'.
Link: https://lkml.kernel.org/r/20220613192301.8817-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit moves code for 'DAMOS_PAGEOUT' handling of the physical
address space monitoring operations set to a separate function so that its
caller, 'damon_pa_apply_scheme()', can be more easily extended for
additional DAMOS actions later.
Link: https://lkml.kernel.org/r/20220613192301.8817-4-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "Extend DAMOS for Proactive LRU-lists Sorting".
Introduction
============
In short, this patchset 1) extends DAMON-based Operation Schemes (DAMOS)
for low overhead data access pattern based LRU-lists sorting, and 2)
implements a static kernel module for easy use of conservatively-tuned
version of that using the extended DAMOS capability.
Background
----------
As page-granularity access checking overhead could be significant on huge
systems, LRU lists are normally not proactively sorted but partially and
reactively sorted for special events including specific user requests,
system calls and memory pressure. As a result, LRU lists are sometimes
not so perfectly prepared to be used as a trustworthy access pattern
source for some situations including reclamation target pages selection
under sudden memory pressure.
DAMON-based Proactive LRU-lists Sorting
---------------------------------------
Because DAMON can identify access patterns of best-effort accuracy while
inducing only user-specified range of overhead, using DAMON for Proactive
LRU-lists Sorting (PLRUS) could be helpful for this situation. The idea
is quite simple. Find hot pages and cold pages using DAMON, and
prioritize hot pages while deprioritizing cold pages on their LRU-lists.
This patchset extends DAMON to support such schemes by introducing a
couple of new DAMOS actions for prioritizing and deprioritizing memory
regions of specific access patterns on their LRU-lists. In detail, this
patchset simply uses 'mark_page_accessed()' and 'deactivate_page()'
functions for prioritization and deprioritization of pages on their LRU
lists, respectively.
To make the scheme easy to use without complex tuning for common
situations, this patchset further implements a static kernel module called
'DAMON_LRU_SORT' using the extended DAMOS functionality. It proactively
sorts LRU-lists using DAMON with conservatively chosen default
hotness/coldness thresholds and small CPU usage quota limit. That is, the
module under its default parameters will make no harm for common situation
but provide some level of benefit for systems having clear hot/cold access
pattern under only memory pressure while consuming only limited small
portion of CPU time.
Related Works
-------------
Proactive reclamation is well known to be helpful for reducing non-optimal
reclamation target selection caused performance drops. However, proactive
reclamation is not a best option for some cases, because it could incur
additional I/O. For an example, it could be prohitive for systems using
storage devices that total number of writes is limited, or cloud block
storages that charges every I/O.
Some proactive reclamation approaches[1,2] induce a level of memory
pressure using memcg files or swappiness while monitoring PSI. As
reclamation target selection is still relying on the original LRU-lists
mechanism, using DAMON-based proactive reclamation before inducing the
proactive reclamation could allow more memory saving with same level of
performance overhead, or less performance overhead with same level of
memory saving.
[1] https://blogs.oracle.com/linux/post/anticipating-your-memory-needs
[2] https://www.pdl.cmu.edu/ftp/NVM/tmo_asplos22.pdf
Evaluation
==========
In short, PLRUS achieves 10% memory PSI (some) reduction, 14% major page
faults reduction, and 3.74% speedup under memory pressure.
Setup
-----
To show the effect of PLRUS, I run PARSEC3 and SPLASH-2X benchmarks under
below variant systems and measure a few metrics including the runtime of
each workload, number of system-wide major page faults, and system-wide
memory PSI (some).
- orig: v5.18-rc4 based mm-unstable kernel + this patchset, but no DAMON scheme
applied.
- mprs: Same to 'orig' but artificial memory pressure is induced.
- plrus: Same to 'mprs' but a radically tuned PLRUS scheme is applied to the
entire physical address space of the system.
For the artificial memory pressure, I set 'memory.limit_in_bytes' to 75%
of the running workload's peak RSS, wait 1 second, remove the pressure by
setting it to 200% of the peak RSS, wait 10 seconds, and repeat the
procedure until the workload finishes[1]. I use zram based swap device.
The tests are automated[2].
[1] https://github.com/awslabs/damon-tests/blob/next/perf/runners/back/0009_memcg_pressure.sh
[2] https://github.com/awslabs/damon-tests/blob/next/perf/full_once_config.sh
Radically Tuned PLRUS
---------------------
To show effect of PLRUS on the PARSEC3/SPLASH-2X workloads which runs for
no long time, we use radically tuned version of PLRUS. The version asks
DAMON to do the proactive LRU-lists sorting as below.
1. Find any memory regions shown some accesses (approximately >=20 accesses per
100 sampling) and prioritize pages of the regions on their LRU lists using
up to 2% CPU time. Under the CPU time limit, prioritize regions having
higher access frequency and kept the access frequency longer first.
2. Find any memory regions shown no access for at least >=5 seconds and
deprioritize pages of the rgions on their LRU lists using up to 2% CPU time.
Under the CPU time limit, deprioritize regions that not accessed for longer
time first.
Results
-------
I repeat the tests 25 times and calculate average of the measured numbers.
The results are as below:
metric orig mprs plrus plrus/mprs
runtime_seconds 190.06 292.83 281.87 0.96
pgmajfaults 852.55 8769420.00 7525040.00 0.86
memory_psi_some_us 106911.00 6943420.00 6220920.00 0.90
The first row is for legend. The first cell shows the metric that the
following cells of the row shows. Second, third, and fourth cells show
the metrics under the configs shown at the first row of the cell, and the
fifth cell shows the metric under 'plrus' divided by the metric under
'mprs'. Second row shows the averaged runtime of the workloads in
seconds. Third row shows the number of system-wide major page faults
while the test was ongoing. Fourth row shows the system-wide memory
pressure stall for some processes in microseconds while the test was
ongoing.
In short, PLRUS achieves 10% memory PSI (some) reduction, 14% major page
faults reduction, and 3.74% speedup under memory pressure. We also
confirmed the CPU usage of kdamond was 2.61% of single CPU, which is below
4% as expected.
Sequence of Patches
===================
The first and second patch cleans up DAMON debugfs interface and
DAMOS_PAGEOUT handling code of physical address space monitoring
operations implementation for easier extension of the code.
The thrid and fourth patches implement a new DAMOS action called
'lru_prio', which prioritizes pages under memory regions which have a
user-specified access pattern, and document it, respectively. The fifth
and sixth patches implement yet another new DAMOS action called
'lru_deprio', which deprioritizes pages under memory regions which have a
user-specified access pattern, and document it, respectively.
The seventh patch implements a static kernel module called
'damon_lru_sort', which utilizes the DAMON-based proactive LRU-lists
sorting under conservatively chosen default parameter. Finally, the
eighth patch documents 'damon_lru_sort'.
This patch (of 8):
DAMON debugfs interface assumes users will write 'damos_action' value
directly to the 'schemes' file. This makes adding new 'damos_action' in
the middle of its definition breaks the backward compatibility of DAMON
debugfs interface, as values of some 'damos_action' could be changed. To
mitigate the situation, this commit adds mappings between the user inputs
and 'damos_action' value and makes DAMON debugfs code uses those.
Link: https://lkml.kernel.org/r/20220613192301.8817-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20220613192301.8817-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
