user/sven/linux.git/include/linux/rmap.h, branch v6.14.8

mm: mass constification of folio/page pointers

2024-11-07T22:38:07Z

Now that page_pgoff() takes const pointers, we can constify the pointers to a lot of functions. Link: https://lkml.kernel.org/r/20241005200121.3231142-5-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton

mm: renovate page_address_in_vma()

2024-11-07T22:38:07Z

This function doesn't modify any of its arguments, so if we make a few other functions take const pointers, we can make page_address_in_vma() take const pointers too. All of its callers have the containing folio already, so pass that in as an argument instead of recalculating it. Also add kernel-doc Link: https://lkml.kernel.org/r/20241005200121.3231142-4-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton

mm: remap unused subpages to shared zeropage when splitting isolated thp

2024-09-09T23:39:03Z

Patch series "mm: split underused THPs", v5. The current upstream default policy for THP is always. However, Meta uses madvise in production as the current THP=always policy vastly overprovisions THPs in sparsely accessed memory areas, resulting in excessive memory pressure and premature OOM killing. Using madvise + relying on khugepaged has certain drawbacks over THP=always. Using madvise hints mean THPs aren't "transparent" and require userspace changes. Waiting for khugepaged to scan memory and collapse pages into THP can be slow and unpredictable in terms of performance (i.e. you dont know when the collapse will happen), while production environments require predictable performance. If there is enough memory available, its better for both performance and predictability to have a THP from fault time, i.e. THP=always rather than wait for khugepaged to collapse it, and deal with sparsely populated THPs when the system is running out of memory. This patch series is an attempt to mitigate the issue of running out of memory when THP is always enabled. During runtime whenever a THP is being faulted in or collapsed by khugepaged, the THP is added to a list. Whenever memory reclaim happens, the kernel runs the deferred_split shrinker which goes through the list and checks if the THP was underused, i.e. how many of the base 4K pages of the entire THP were zero-filled. If this number goes above a certain threshold, the shrinker will attempt to split that THP. Then at remap time, the pages that were zero-filled are mapped to the shared zeropage, hence saving memory. This method avoids the downside of wasting memory in areas where THP is sparsely filled when THP is always enabled, while still providing the upside THPs like reduced TLB misses without having to use madvise. Meta production workloads that were CPU bound (>99% CPU utilzation) were tested with THP shrinker. The results after 2 hours are as follows: | THP=madvise | THP=always | THP=always | | | + shrinker series | | | + max_ptes_none=409 ----------------------------------------------------------------------------- Performance improvement | - | +1.8% | +1.7% (over THP=madvise) | | | ----------------------------------------------------------------------------- Memory usage | 54.6G | 58.8G (+7.7%) | 55.9G (+2.4%) ----------------------------------------------------------------------------- max_ptes_none=409 means that any THP that has more than 409 out of 512 (80%) zero filled filled pages will be split. To test out the patches, the below commands without the shrinker will invoke OOM killer immediately and kill stress, but will not fail with the shrinker: echo 450 > /sys/kernel/mm/transparent_hugepage/khugepaged/max_ptes_none mkdir /sys/fs/cgroup/test echo $$ > /sys/fs/cgroup/test/cgroup.procs echo 20M > /sys/fs/cgroup/test/memory.max echo 0 > /sys/fs/cgroup/test/memory.swap.max # allocate twice memory.max for each stress worker and touch 40/512 of # each THP, i.e. vm-stride 50K. # With the shrinker, max_ptes_none of 470 and below won't invoke OOM # killer. # Without the shrinker, OOM killer is invoked immediately irrespective # of max_ptes_none value and kills stress. stress --vm 1 --vm-bytes 40M --vm-stride 50K This patch (of 5): Here being unused means containing only zeros and inaccessible to userspace. When splitting an isolated thp under reclaim or migration, the unused subpages can be mapped to the shared zeropage, hence saving memory. This is particularly helpful when the internal fragmentation of a thp is high, i.e. it has many untouched subpages. This is also a prerequisite for THP low utilization shrinker which will be introduced in later patches, where underutilized THPs are split, and the zero-filled pages are freed saving memory. Link: https://lkml.kernel.org/r/20240830100438.3623486-1-usamaarif642@gmail.com Link: https://lkml.kernel.org/r/20240830100438.3623486-3-usamaarif642@gmail.com Signed-off-by: Yu Zhao Signed-off-by: Usama Arif Tested-by: Shuang Zhai Cc: Alexander Zhu Cc: Barry Song Cc: David Hildenbrand Cc: Domenico Cerasuolo Cc: Johannes Weiner Cc: Jonathan Corbet Cc: Kairui Song Cc: Matthew Wilcox Cc: Mike Rapoport Cc: Nico Pache Cc: Rik van Riel Cc: Roman Gushchin Cc: Ryan Roberts Cc: Shakeel Butt Cc: Shuang Zhai Cc: Hugh Dickins Signed-off-by: Andrew Morton

mm/rmap: use folio->_mapcount for small folios

2024-09-04T04:15:37Z

We have some cases left whereby we operate on small folios and still refer to page->_mapcount. Let's just use folio->_mapcount instead, which currently still overlays page->_mapcount, so no change. This change will make it easier to later spot any remaining users of page->_mapcount that target tail pages. Link: https://lkml.kernel.org/r/20240816103246.719209-1-david@redhat.com Signed-off-by: David Hildenbrand Cc: Matthew Wilcox Signed-off-by: Andrew Morton

mm: extend rmap flags arguments for folio_add_new_anon_rmap

2024-07-04T02:30:18Z

Patch series "mm: clarify folio_add_new_anon_rmap() and __folio_add_anon_rmap()", v2. This patchset is preparatory work for mTHP swapin. folio_add_new_anon_rmap() assumes that new anon rmaps are always exclusive. However, this assumption doesn’t hold true for cases like do_swap_page(), where a new anon might be added to the swapcache and is not necessarily exclusive. The patchset extends the rmap flags to allow folio_add_new_anon_rmap() to handle both exclusive and non-exclusive new anon folios. The do_swap_page() function is updated to use this extended API with rmap flags. Consequently, all new anon folios now consistently use folio_add_new_anon_rmap(). The special case for !folio_test_anon() in __folio_add_anon_rmap() can be safely removed. In conclusion, new anon folios always use folio_add_new_anon_rmap(), regardless of exclusivity. Old anon folios continue to use __folio_add_anon_rmap() via folio_add_anon_rmap_pmd() and folio_add_anon_rmap_ptes(). This patch (of 3): In the case of a swap-in, a new anonymous folio is not necessarily exclusive. This patch updates the rmap flags to allow a new anonymous folio to be treated as either exclusive or non-exclusive. To maintain the existing behavior, we always use EXCLUSIVE as the default setting. [akpm@linux-foundation.org: cleanup and constifications per David and akpm] [v-songbaohua@oppo.com: fix missing doc for flags of folio_add_new_anon_rmap()] Link: https://lkml.kernel.org/r/20240619210641.62542-1-21cnbao@gmail.com [v-songbaohua@oppo.com: enhance doc for extend rmap flags arguments for folio_add_new_anon_rmap] Link: https://lkml.kernel.org/r/20240622030256.43775-1-21cnbao@gmail.com Link: https://lkml.kernel.org/r/20240617231137.80726-1-21cnbao@gmail.com Link: https://lkml.kernel.org/r/20240617231137.80726-2-21cnbao@gmail.com Signed-off-by: Barry Song Suggested-by: David Hildenbrand Tested-by: Shuai Yuan Acked-by: David Hildenbrand Cc: Baolin Wang Cc: Chris Li Cc: "Huang, Ying" Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Ryan Roberts Cc: Suren Baghdasaryan Cc: Yang Shi Cc: Yosry Ahmed Cc: Yu Zhao Signed-off-by: Andrew Morton

mm: remove page_mkclean()

2024-07-04T02:30:17Z

There are no more users of page_mkclean(), remove it and update the document and comment. Link: https://lkml.kernel.org/r/20240604114822.2089819-5-wangkefeng.wang@huawei.com Signed-off-by: Kefeng Wang Acked-by: David Hildenbrand Cc: Daniel Vetter Cc: Helge Deller Cc: Jonathan Corbet Cc: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton

mm/memory-failure: move some function declarations into internal.h

2024-07-04T02:30:11Z

There are some functions only used inside mm. Move them into internal.h. No functional change intended. Link: https://lkml.kernel.org/r/20240612071835.157004-11-linmiaohe@huawei.com Signed-off-by: Miaohe Lin Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202405251049.hxjwX7zO-lkp@intel.com/ Cc: Borislav Petkov (AMD) Cc: David Hildenbrand Cc: Naoya Horiguchi Cc: Tony Luck Signed-off-by: Andrew Morton

mm/rmap: integrate PMD-mapped folio splitting into pagewalk loop

2024-07-04T02:30:08Z

In preparation for supporting try_to_unmap_one() to unmap PMD-mapped folios, start the pagewalk first, then call split_huge_pmd_address() to split the folio. Link: https://lkml.kernel.org/r/20240614015138.31461-3-ioworker0@gmail.com Signed-off-by: Lance Yang Suggested-by: David Hildenbrand Acked-by: David Hildenbrand Suggested-by: Baolin Wang Acked-by: Zi Yan Cc: Bang Li Cc: Barry Song Cc: Fangrui Song Cc: Jeff Xie Cc: Kefeng Wang Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Minchan Kim Cc: Muchun Song Cc: Peter Xu Cc: Ryan Roberts Cc: SeongJae Park Cc: Yang Shi Cc: Yin Fengwei Cc: Zach O'Keefe Signed-off-by: Andrew Morton

rmap: remove DEFINE_PAGE_VMA_WALK()

2024-07-04T02:29:59Z

This are no users since commit 40d707f33db5 ("mm/ksm: use folio in write_protect_page"), so remove DEFINE_PAGE_VMA_WALK(). Link: https://lkml.kernel.org/r/20240524053618.208895-1-wangkefeng.wang@huawei.com Signed-off-by: Kefeng Wang Reviewed-by: David Hildenbrand Cc: Alex Shi Cc: Matthew Wilcox Signed-off-by: Andrew Morton

mm/rmap: sanity check that zeropages are not passed to RMAP

2024-07-04T02:29:56Z

Using insert_page() we might have previously ended up passing the zeropage into rmap code. Make sure that won't happen again. Note that we won't check the huge zeropage for now, which might still end up in RMAP code. Link: https://lkml.kernel.org/r/20240522125713.775114-4-david@redhat.com Signed-off-by: David Hildenbrand Cc: Dan Williams Cc: Vincent Donnefort Signed-off-by: Andrew Morton