user/sven/linux.git/include/linux/swap.h, branch v6.10.6

cachestat: do not flush stats in recency check

2024-07-04T05:40:37Z

syzbot detects that cachestat() is flushing stats, which can sleep, in its RCU read section (see [1]). This is done in the workingset_test_recent() step (which checks if the folio's eviction is recent). Move the stat flushing step to before the RCU read section of cachestat, and skip stat flushing during the recency check. [1]: https://lore.kernel.org/cgroups/000000000000f71227061bdf97e0@google.com/ Link: https://lkml.kernel.org/r/20240627201737.3506959-1-nphamcs@gmail.com Fixes: b00684722262 ("mm: workingset: move the stats flush into workingset_test_recent()") Signed-off-by: Nhat Pham Reported-by: syzbot+b7f13b2d0cc156edf61a@syzkaller.appspotmail.com Closes: https://lore.kernel.org/cgroups/000000000000f71227061bdf97e0@google.com/ Debugged-by: Johannes Weiner Suggested-by: Johannes Weiner Acked-by: Johannes Weiner Acked-by: Shakeel Butt Cc: Al Viro Cc: David Hildenbrand Cc: "Huang, Ying" Cc: Kairui Song Cc: Matthew Wilcox (Oracle) Cc: Ryan Roberts Cc: Yosry Ahmed Cc: [6.8+] Signed-off-by: Andrew Morton

Merge tag 'pull-set_blocksize' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2024-05-21T15:34:51Z

Pull vfs blocksize updates from Al Viro: "This gets rid of bogus set_blocksize() uses, switches it over to be based on a 'struct file *' and verifies that the caller has the device opened exclusively" * tag 'pull-set_blocksize' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: make set_blocksize() fail unless block device is opened exclusive set_blocksize(): switch to passing struct file * btrfs_get_bdev_and_sb(): call set_blocksize() only for exclusive opens swsusp: don't bother with setting block size zram: don't bother with reopening - just use O_EXCL for open swapon(2): open swap with O_EXCL swapon(2)/swapoff(2): don't bother with block size pktcdvd: sort set_blocksize() calls out bcache_register(): don't bother with set_blocksize()

swapon(2): open swap with O_EXCL

2024-05-02T21:23:30Z

... eliminating the need to reopen block devices so they could be exclusively held. Reviewed-by: Christoph Hellwig Reviewed-by: Christian Brauner Signed-off-by: Al Viro

swapon(2)/swapoff(2): don't bother with block size

2024-05-02T21:23:30Z

once upon a time that used to matter; these days we do swap IO for swap devices at the level that doesn't give a damn about block size, buffer_head or anything of that sort - just attach the page to bio, set the location and size (the latter to PAGE_SIZE) and feed into queue. Reviewed-by: Christoph Hellwig Reviewed-by: Christian Brauner Signed-off-by: Al Viro

mm: swap: allow storage of all mTHP orders

2024-04-26T03:56:37Z

Multi-size THP enables performance improvements by allocating large, pte-mapped folios for anonymous memory. However I've observed that on an arm64 system running a parallel workload (e.g. kernel compilation) across many cores, under high memory pressure, the speed regresses. This is due to bottlenecking on the increased number of TLBIs added due to all the extra folio splitting when the large folios are swapped out. Therefore, solve this regression by adding support for swapping out mTHP without needing to split the folio, just like is already done for PMD-sized THP. This change only applies when CONFIG_THP_SWAP is enabled, and when the swap backing store is a non-rotating block device. These are the same constraints as for the existing PMD-sized THP swap-out support. Note that no attempt is made to swap-in (m)THP here - this is still done page-by-page, like for PMD-sized THP. But swapping-out mTHP is a prerequisite for swapping-in mTHP. The main change here is to improve the swap entry allocator so that it can allocate any power-of-2 number of contiguous entries between [1, (1 << PMD_ORDER)]. This is done by allocating a cluster for each distinct order and allocating sequentially from it until the cluster is full. This ensures that we don't need to search the map and we get no fragmentation due to alignment padding for different orders in the cluster. If there is no current cluster for a given order, we attempt to allocate a free cluster from the list. If there are no free clusters, we fail the allocation and the caller can fall back to splitting the folio and allocates individual entries (as per existing PMD-sized THP fallback). The per-order current clusters are maintained per-cpu using the existing infrastructure. This is done to avoid interleving pages from different tasks, which would prevent IO being batched. This is already done for the order-0 allocations so we follow the same pattern. As is done for order-0 per-cpu clusters, the scanner now can steal order-0 entries from any per-cpu-per-order reserved cluster. This ensures that when the swap file is getting full, space doesn't get tied up in the per-cpu reserves. This change only modifies swap to be able to accept any order mTHP. It doesn't change the callers to elide doing the actual split. That will be done in separate changes. Link: https://lkml.kernel.org/r/20240408183946.2991168-6-ryan.roberts@arm.com Signed-off-by: Ryan Roberts Reviewed-by: "Huang, Ying" Cc: Barry Song <21cnbao@gmail.com> Cc: Barry Song Cc: Chris Li Cc: David Hildenbrand Cc: Gao Xiang Cc: Kefeng Wang Cc: Lance Yang Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Yang Shi Cc: Yu Zhao Signed-off-by: Andrew Morton

mm: swap: update get_swap_pages() to take folio order

2024-04-26T03:56:37Z

We are about to allow swap storage of any mTHP size. To prepare for that, let's change get_swap_pages() to take a folio order parameter instead of nr_pages. This makes the interface self-documenting; a power-of-2 number of pages must be provided. We will also need the order internally so this simplifies accessing it. Link: https://lkml.kernel.org/r/20240408183946.2991168-5-ryan.roberts@arm.com Signed-off-by: Ryan Roberts Reviewed-by: "Huang, Ying" Reviewed-by: David Hildenbrand Cc: Barry Song <21cnbao@gmail.com> Cc: Barry Song Cc: Chris Li Cc: Gao Xiang Cc: Kefeng Wang Cc: Lance Yang Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Yang Shi Cc: Yu Zhao Signed-off-by: Andrew Morton

mm: swap: simplify struct percpu_cluster

2024-04-26T03:56:37Z

struct percpu_cluster stores the index of cpu's current cluster and the offset of the next entry that will be allocated for the cpu. These two pieces of information are redundant because the cluster index is just (offset / SWAPFILE_CLUSTER). The only reason for explicitly keeping the cluster index is because the structure used for it also has a flag to indicate "no cluster". However this data structure also contains a spin lock, which is never used in this context, as a side effect the code copies the spinlock_t structure, which is questionable coding practice in my view. So let's clean this up and store only the next offset, and use a sentinal value (SWAP_NEXT_INVALID) to indicate "no cluster". SWAP_NEXT_INVALID is chosen to be 0, because 0 will never be seen legitimately; The first page in the swap file is the swap header, which is always marked bad to prevent it from being allocated as an entry. This also prevents the cluster to which it belongs being marked free, so it will never appear on the free list. This change saves 16 bytes per cpu. And given we are shortly going to extend this mechanism to be per-cpu-AND-per-order, we will end up saving 16 * 9 = 144 bytes per cpu, which adds up if you have 256 cpus in the system. Link: https://lkml.kernel.org/r/20240408183946.2991168-4-ryan.roberts@arm.com Signed-off-by: Ryan Roberts Reviewed-by: "Huang, Ying" Cc: Barry Song <21cnbao@gmail.com> Cc: Barry Song Cc: Chris Li Cc: David Hildenbrand Cc: Gao Xiang Cc: Kefeng Wang Cc: Lance Yang Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Yang Shi Cc: Yu Zhao Signed-off-by: Andrew Morton

mm: swap: free_swap_and_cache_nr() as batched free_swap_and_cache()

2024-04-26T03:56:37Z

Now that we no longer have a convenient flag in the cluster to determine if a folio is large, free_swap_and_cache() will take a reference and lock a large folio much more often, which could lead to contention and (e.g.) failure to split large folios, etc. Let's solve that problem by batch freeing swap and cache with a new function, free_swap_and_cache_nr(), to free a contiguous range of swap entries together. This allows us to first drop a reference to each swap slot before we try to release the cache folio. This means we only try to release the folio once, only taking the reference and lock once - much better than the previous 512 times for the 2M THP case. Contiguous swap entries are gathered in zap_pte_range() and madvise_free_pte_range() in a similar way to how present ptes are already gathered in zap_pte_range(). While we are at it, let's simplify by converting the return type of both functions to void. The return value was used only by zap_pte_range() to print a bad pte, and was ignored by everyone else, so the extra reporting wasn't exactly guaranteed. We will still get the warning with most of the information from get_swap_device(). With the batch version, we wouldn't know which pte was bad anyway so could print the wrong one. [ryan.roberts@arm.com: fix a build warning on parisc] Link: https://lkml.kernel.org/r/20240409111840.3173122-1-ryan.roberts@arm.com Link: https://lkml.kernel.org/r/20240408183946.2991168-3-ryan.roberts@arm.com Signed-off-by: Ryan Roberts Acked-by: David Hildenbrand Cc: Barry Song <21cnbao@gmail.com> Cc: Barry Song Cc: Chris Li Cc: Gao Xiang Cc: "Huang, Ying" Cc: Kefeng Wang Cc: Lance Yang Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Yang Shi Cc: Yu Zhao Signed-off-by: Andrew Morton

mm: swap: remove CLUSTER_FLAG_HUGE from swap_cluster_info:flags

2024-04-26T03:56:36Z

Patch series "Swap-out mTHP without splitting", v7. This series adds support for swapping out multi-size THP (mTHP) without needing to first split the large folio via split_huge_page_to_list_to_order(). It closely follows the approach already used to swap-out PMD-sized THP. There are a couple of reasons for swapping out mTHP without splitting: - Performance: It is expensive to split a large folio and under extreme memory pressure some workloads regressed performance when using 64K mTHP vs 4K small folios because of this extra cost in the swap-out path. This series not only eliminates the regression but makes it faster to swap out 64K mTHP vs 4K small folios. - Memory fragmentation avoidance: If we can avoid splitting a large folio memory is less likely to become fragmented, making it easier to re-allocate a large folio in future. - Performance: Enables a separate series [7] to swap-in whole mTHPs, which means we won't lose the TLB-efficiency benefits of mTHP once the memory has been through a swap cycle. I've done what I thought was the smallest change possible, and as a result, this approach is only employed when the swap is backed by a non-rotating block device (just as PMD-sized THP is supported today). Discussion against the RFC concluded that this is sufficient. Performance Testing =================== I've run some swap performance tests on Ampere Altra VM (arm64) with 8 CPUs. The VM is set up with a 35G block ram device as the swap device and the test is run from inside a memcg limited to 40G memory. I've then run `usemem` from vm-scalability with 70 processes, each allocating and writing 1G of memory. I've repeated everything 6 times and taken the mean performance improvement relative to 4K page baseline: | alloc size | baseline | + this series | | | mm-unstable (~v6.9-rc1) | | |:-----------|------------------------:|------------------------:| | 4K Page | 0.0% | 1.3% | | 64K THP | -13.6% | 46.3% | | 2M THP | 91.4% | 89.6% | So with this change, the 64K swap performance goes from a 14% regression to a 46% improvement. While 2M shows a small regression I'm confident that this is just noise. [1] https://lore.kernel.org/linux-mm/20231010142111.3997780-1-ryan.roberts@arm.com/ [2] https://lore.kernel.org/linux-mm/20231017161302.2518826-1-ryan.roberts@arm.com/ [3] https://lore.kernel.org/linux-mm/20231025144546.577640-1-ryan.roberts@arm.com/ [4] https://lore.kernel.org/linux-mm/20240311150058.1122862-1-ryan.roberts@arm.com/ [5] https://lore.kernel.org/linux-mm/20240327144537.4165578-1-ryan.roberts@arm.com/ [6] https://lore.kernel.org/linux-mm/20240403114032.1162100-1-ryan.roberts@arm.com/ [7] https://lore.kernel.org/linux-mm/20240304081348.197341-1-21cnbao@gmail.com/ [8] https://lore.kernel.org/linux-mm/CAGsJ_4yMOow27WDvN2q=E4HAtDd2PJ=OQ5Pj9DG+6FLWwNuXUw@mail.gmail.com/ [9] https://lore.kernel.org/linux-mm/579d5127-c763-4001-9625-4563a9316ac3@redhat.com/ This patch (of 7): As preparation for supporting small-sized THP in the swap-out path, without first needing to split to order-0, Remove the CLUSTER_FLAG_HUGE, which, when present, always implies PMD-sized THP, which is the same as the cluster size. The only use of the flag was to determine whether a swap entry refers to a single page or a PMD-sized THP in swap_page_trans_huge_swapped(). Instead of relying on the flag, we now pass in order, which originates from the folio's order. This allows the logic to work for folios of any order. The one snag is that one of the swap_page_trans_huge_swapped() call sites does not have the folio. But it was only being called there to shortcut a call __try_to_reclaim_swap() in some cases. __try_to_reclaim_swap() gets the folio and (via some other functions) calls swap_page_trans_huge_swapped(). So I've removed the problematic call site and believe the new logic should be functionally equivalent. That said, removing the fast path means that we will take a reference and trylock a large folio much more often, which we would like to avoid. The next patch will solve this. Removing CLUSTER_FLAG_HUGE also means we can remove split_swap_cluster() which used to be called during folio splitting, since split_swap_cluster()'s only job was to remove the flag. Link: https://lkml.kernel.org/r/20240408183946.2991168-1-ryan.roberts@arm.com Link: https://lkml.kernel.org/r/20240408183946.2991168-2-ryan.roberts@arm.com Signed-off-by: Ryan Roberts Reviewed-by: "Huang, Ying" Acked-by: Chris Li Acked-by: David Hildenbrand Cc: Barry Song <21cnbao@gmail.com> Cc: Gao Xiang Cc: Kefeng Wang Cc: Lance Yang Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Yang Shi Cc: Yu Zhao Cc: Barry Song Signed-off-by: Andrew Morton

Merge tag 'mm-stable-2024-03-13-20-04' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2024-03-15T00:43:30Z

Pull MM updates from Andrew Morton: - Sumanth Korikkar has taught s390 to allocate hotplug-time page frames from hotplugged memory rather than only from main memory. Series "implement "memmap on memory" feature on s390". - More folio conversions from Matthew Wilcox in the series "Convert memcontrol charge moving to use folios" "mm: convert mm counter to take a folio" - Chengming Zhou has optimized zswap's rbtree locking, providing significant reductions in system time and modest but measurable reductions in overall runtimes. The series is "mm/zswap: optimize the scalability of zswap rb-tree". - Chengming Zhou has also provided the series "mm/zswap: optimize zswap lru list" which provides measurable runtime benefits in some swap-intensive situations. - And Chengming Zhou further optimizes zswap in the series "mm/zswap: optimize for dynamic zswap_pools". Measured improvements are modest. - zswap cleanups and simplifications from Yosry Ahmed in the series "mm: zswap: simplify zswap_swapoff()". - In the series "Add DAX ABI for memmap_on_memory", Vishal Verma has contributed several DAX cleanups as well as adding a sysfs tunable to control the memmap_on_memory setting when the dax device is hotplugged as system memory. - Johannes Weiner has added the large series "mm: zswap: cleanups", which does that. - More DAMON work from SeongJae Park in the series "mm/damon: make DAMON debugfs interface deprecation unignorable" "selftests/damon: add more tests for core functionalities and corner cases" "Docs/mm/damon: misc readability improvements" "mm/damon: let DAMOS feeds and tame/auto-tune itself" - In the series "mm/mempolicy: weighted interleave mempolicy and sysfs extension" Rakie Kim has developed a new mempolicy interleaving policy wherein we allocate memory across nodes in a weighted fashion rather than uniformly. This is beneficial in heterogeneous memory environments appearing with CXL. - Christophe Leroy has contributed some cleanup and consolidation work against the ARM pagetable dumping code in the series "mm: ptdump: Refactor CONFIG_DEBUG_WX and check_wx_pages debugfs attribute". - Luis Chamberlain has added some additional xarray selftesting in the series "test_xarray: advanced API multi-index tests". - Muhammad Usama Anjum has reworked the selftest code to make its human-readable output conform to the TAP ("Test Anything Protocol") format. Amongst other things, this opens up the use of third-party tools to parse and process out selftesting results. - Ryan Roberts has added fork()-time PTE batching of THP ptes in the series "mm/memory: optimize fork() with PTE-mapped THP". Mainly targeted at arm64, this significantly speeds up fork() when the process has a large number of pte-mapped folios. - David Hildenbrand also gets in on the THP pte batching game in his series "mm/memory: optimize unmap/zap with PTE-mapped THP". It implements batching during munmap() and other pte teardown situations. The microbenchmark improvements are nice. - And in the series "Transparent Contiguous PTEs for User Mappings" Ryan Roberts further utilizes arm's pte's contiguous bit ("contpte mappings"). Kernel build times on arm64 improved nicely. Ryan's series "Address some contpte nits" provides some followup work. - In the series "mm/hugetlb: Restore the reservation" Breno Leitao has fixed an obscure hugetlb race which was causing unnecessary page faults. He has also added a reproducer under the selftest code. - In the series "selftests/mm: Output cleanups for the compaction test", Mark Brown did what the title claims. - Kinsey Ho has added the series "mm/mglru: code cleanup and refactoring". - Even more zswap material from Nhat Pham. The series "fix and extend zswap kselftests" does as claimed. - In the series "Introduce cpu_dcache_is_aliasing() to fix DAX regression" Mathieu Desnoyers has cleaned up and fixed rather a mess in our handling of DAX on archiecctures which have virtually aliasing data caches. The arm architecture is the main beneficiary. - Lokesh Gidra's series "per-vma locks in userfaultfd" provides dramatic improvements in worst-case mmap_lock hold times during certain userfaultfd operations. - Some page_owner enhancements and maintenance work from Oscar Salvador in his series "page_owner: print stacks and their outstanding allocations" "page_owner: Fixup and cleanup" - Uladzislau Rezki has contributed some vmalloc scalability improvements in his series "Mitigate a vmap lock contention". It realizes a 12x improvement for a certain microbenchmark. - Some kexec/crash cleanup work from Baoquan He in the series "Split crash out from kexec and clean up related config items". - Some zsmalloc maintenance work from Chengming Zhou in the series "mm/zsmalloc: fix and optimize objects/page migration" "mm/zsmalloc: some cleanup for get/set_zspage_mapping()" - Zi Yan has taught the MM to perform compaction on folios larger than order=0. This a step along the path to implementaton of the merging of large anonymous folios. The series is named "Enable >0 order folio memory compaction". - Christoph Hellwig has done quite a lot of cleanup work in the pagecache writeback code in his series "convert write_cache_pages() to an iterator". - Some modest hugetlb cleanups and speedups in Vishal Moola's series "Handle hugetlb faults under the VMA lock". - Zi Yan has changed the page splitting code so we can split huge pages into sizes other than order-0 to better utilize large folios. The series is named "Split a folio to any lower order folios". - David Hildenbrand has contributed the series "mm: remove total_mapcount()", a cleanup. - Matthew Wilcox has sought to improve the performance of bulk memory freeing in his series "Rearrange batched folio freeing". - Gang Li's series "hugetlb: parallelize hugetlb page init on boot" provides large improvements in bootup times on large machines which are configured to use large numbers of hugetlb pages. - Matthew Wilcox's series "PageFlags cleanups" does that. - Qi Zheng's series "minor fixes and supplement for ptdesc" does that also. S390 is affected. - Cleanups to our pagemap utility functions from Peter Xu in his series "mm/treewide: Replace pXd_large() with pXd_leaf()". - Nico Pache has fixed a few things with our hugepage selftests in his series "selftests/mm: Improve Hugepage Test Handling in MM Selftests". - Also, of course, many singleton patches to many things. Please see the individual changelogs for details. * tag 'mm-stable-2024-03-13-20-04' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (435 commits) mm/zswap: remove the memcpy if acomp is not sleepable crypto: introduce: acomp_is_async to expose if comp drivers might sleep memtest: use {READ,WRITE}_ONCE in memory scanning mm: prohibit the last subpage from reusing the entire large folio mm: recover pud_leaf() definitions in nopmd case selftests/mm: skip the hugetlb-madvise tests on unmet hugepage requirements selftests/mm: skip uffd hugetlb tests with insufficient hugepages selftests/mm: dont fail testsuite due to a lack of hugepages mm/huge_memory: skip invalid debugfs new_order input for folio split mm/huge_memory: check new folio order when split a folio mm, vmscan: retry kswapd's priority loop with cache_trim_mode off on failure mm: add an explicit smp_wmb() to UFFDIO_CONTINUE mm: fix list corruption in put_pages_list mm: remove folio from deferred split list before uncharging it filemap: avoid unnecessary major faults in filemap_fault() mm,page_owner: drop unnecessary check mm,page_owner: check for null stack_record before bumping its refcount mm: swap: fix race between free_swap_and_cache() and swapoff() mm/treewide: align up pXd_leaf() retval across archs mm/treewide: drop pXd_large() ...