kernel/linux.git/mm/vmstat.c, branch v5.10.257

arm: remove CONFIG_ARCH_HAS_HOLES_MEMORYMODEL

2022-05-15T18:00:09+00:00

commit 5e545df3292fbd3d5963c68980f1527ead2a2b3f upstream. ARM is the only architecture that defines CONFIG_ARCH_HAS_HOLES_MEMORYMODEL which in turn enables memmap_valid_within() function that is intended to verify existence of struct page associated with a pfn when there are holes in the memory map. However, the ARCH_HAS_HOLES_MEMORYMODEL also enables HAVE_ARCH_PFN_VALID and arch-specific pfn_valid() implementation that also deals with the holes in the memory map. The only two users of memmap_valid_within() call this function after a call to pfn_valid() so the memmap_valid_within() check becomes redundant. Remove CONFIG_ARCH_HAS_HOLES_MEMORYMODEL and memmap_valid_within() and rely entirely on ARM's implementation of pfn_valid() that is now enabled unconditionally. Link: https://lkml.kernel.org/r/20201101170454.9567-9-rppt@kernel.org Signed-off-by: Mike Rapoport Cc: Alexey Dobriyan Cc: Catalin Marinas Cc: Geert Uytterhoeven Cc: Greg Ungerer Cc: John Paul Adrian Glaubitz Cc: Jonathan Corbet Cc: Matt Turner Cc: Meelis Roos Cc: Michael Schmitz Cc: Russell King Cc: Tony Luck Cc: Vineet Gupta Cc: Will Deacon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Reported-by: kernel test robot Fixes: 8dd559d53b3b ("arm: ioremap: don't abuse pfn_valid() to check if pfn is in RAM") Signed-off-by: Mike Rapoport Signed-off-by: Greg Kroah-Hartman

mm/vmstat.c: use helper macro abs()

2020-10-16T18:11:17+00:00

Use helper macro abs() to simplify the "x > t || x < -t" cmp. Signed-off-by: Miaohe Lin Signed-off-by: Andrew Morton Reviewed-by: Andrew Morton Link: https://lkml.kernel.org/r/20200905084008.15748-1-linmiaohe@huawei.com Signed-off-by: Linus Torvalds

Merge branch 'simplify-do_wp_page'

2020-09-04T16:31:54+00:00

Merge emailed patches from Peter Xu: "This is a small series that I picked up from Linus's suggestion to simplify cow handling (and also make it more strict) by checking against page refcounts rather than mapcounts. This makes uffd-wp work again (verified by running upmapsort)" Note: this is horrendously bad timing, and making this kind of fundamental vm change after -rc3 is not at all how things should work. The saving grace is that it really is a a nice simplification: 8 files changed, 29 insertions(+), 120 deletions(-) The reason for the bad timing is that it turns out that commit 17839856fd58 ("gup: document and work around 'COW can break either way' issue" broke not just UFFD functionality (as Peter noticed), but Mikulas Patocka also reports that it caused issues for strace when running in a DAX environment with ext4 on a persistent memory setup. And we can't just revert that commit without re-introducing the original issue that is a potential security hole, so making COW stricter (and in the process much simpler) is a step to then undoing the forced COW that broke other uses. Link: https://lore.kernel.org/lkml/alpine.LRH.2.02.2009031328040.6929@file01.intranet.prod.int.rdu2.redhat.com/ * emailed patches from Peter Xu : mm: Add PGREUSE counter mm/gup: Remove enfornced COW mechanism mm/ksm: Remove reuse_ksm_page() mm: do_wp_page() simplification

mm: Add PGREUSE counter

2020-09-04T16:25:20+00:00

This accounts for wp_page_reuse() case, where we reused a page for COW. Signed-off-by: Peter Xu Signed-off-by: Linus Torvalds

Revert "mm/vmstat.c: do not show lowmem reserve protection information of empty zone"

2020-08-15T02:56:56+00:00

This reverts commit 26e7deadaae175. Sonny reported that one of their tests started failing on the latest kernel on their Chrome OS platform. The root cause is that the above commit removed the protection line of empty zone, while the parser used in the test relies on the protection line to mark the end of each zone. Let's revert it to avoid breaking userspace testing or applications. Fixes: 26e7deadaae175 ("mm/vmstat.c: do not show lowmem reserve protection information of empty zone)" Reported-by: Sonny Rao Signed-off-by: Baoquan He Signed-off-by: Andrew Morton Reviewed-by: David Hildenbrand Acked-by: David Rientjes Cc: [5.8.x] Link: http://lkml.kernel.org/r/20200811075412.12872-1-bhe@redhat.com Signed-off-by: Linus Torvalds

mm/vmstat: add events for THP migration without split

2020-08-12T17:57:57+00:00

Add following new vmstat events which will help in validating THP migration without split. Statistics reported through these new VM events will help in performance debugging. 1. THP_MIGRATION_SUCCESS 2. THP_MIGRATION_FAILURE 3. THP_MIGRATION_SPLIT In addition, these new events also update normal page migration statistics appropriately via PGMIGRATE_SUCCESS and PGMIGRATE_FAILURE. While here, this updates current trace event 'mm_migrate_pages' to accommodate now available THP statistics. [akpm@linux-foundation.org: s/hpage_nr_pages/thp_nr_pages/] [ziy@nvidia.com: v2] Link: http://lkml.kernel.org/r/C5E3C65C-8253-4638-9D3C-71A61858BB8B@nvidia.com [anshuman.khandual@arm.com: s/thp_nr_pages/hpage_nr_pages/] Link: http://lkml.kernel.org/r/1594287583-16568-1-git-send-email-anshuman.khandual@arm.com Signed-off-by: Anshuman Khandual Signed-off-by: Zi Yan Signed-off-by: Andrew Morton Reviewed-by: Daniel Jordan Cc: Hugh Dickins Cc: Matthew Wilcox Cc: Zi Yan Cc: John Hubbard Cc: Naoya Horiguchi Link: http://lkml.kernel.org/r/1594080415-27924-1-git-send-email-anshuman.khandual@arm.com Signed-off-by: Linus Torvalds

mm: use unsigned types for fragmentation score

2020-08-12T17:57:56+00:00

Proactive compaction uses per-node/zone "fragmentation score" which is always in range [0, 100], so use unsigned type of these scores as well as for related constants. Signed-off-by: Nitin Gupta Signed-off-by: Andrew Morton Reviewed-by: Baoquan He Cc: Luis Chamberlain Cc: Kees Cook Cc: Iurii Zaikin Cc: Vlastimil Babka Cc: Joonsoo Kim Link: http://lkml.kernel.org/r/20200618010319.13159-1-nigupta@nvidia.com Signed-off-by: Linus Torvalds

mm: proactive compaction

2020-08-12T17:57:56+00:00

For some applications, we need to allocate almost all memory as hugepages. However, on a running system, higher-order allocations can fail if the memory is fragmented. Linux kernel currently does on-demand compaction as we request more hugepages, but this style of compaction incurs very high latency. Experiments with one-time full memory compaction (followed by hugepage allocations) show that kernel is able to restore a highly fragmented memory state to a fairly compacted memory state within <1 sec for a 32G system. Such data suggests that a more proactive compaction can help us allocate a large fraction of memory as hugepages keeping allocation latencies low. For a more proactive compaction, the approach taken here is to define a new sysctl called 'vm.compaction_proactiveness' which dictates bounds for external fragmentation which kcompactd tries to maintain. The tunable takes a value in range [0, 100], with a default of 20. Note that a previous version of this patch [1] was found to introduce too many tunables (per-order extfrag{low, high}), but this one reduces them to just one sysctl. Also, the new tunable is an opaque value instead of asking for specific bounds of "external fragmentation", which would have been difficult to estimate. The internal interpretation of this opaque value allows for future fine-tuning. Currently, we use a simple translation from this tunable to [low, high] "fragmentation score" thresholds (low=100-proactiveness, high=low+10%). The score for a node is defined as weighted mean of per-zone external fragmentation. A zone's present_pages determines its weight. To periodically check per-node score, we reuse per-node kcompactd threads, which are woken up every 500 milliseconds to check the same. If a node's score exceeds its high threshold (as derived from user-provided proactiveness value), proactive compaction is started until its score reaches its low threshold value. By default, proactiveness is set to 20, which implies threshold values of low=80 and high=90. This patch is largely based on ideas from Michal Hocko [2]. See also the LWN article [3]. Performance data ================ System: x64_64, 1T RAM, 80 CPU threads. Kernel: 5.6.0-rc3 + this patch echo madvise | sudo tee /sys/kernel/mm/transparent_hugepage/enabled echo madvise | sudo tee /sys/kernel/mm/transparent_hugepage/defrag Before starting the driver, the system was fragmented from a userspace program that allocates all memory and then for each 2M aligned section, frees 3/4 of base pages using munmap. The workload is mainly anonymous userspace pages, which are easy to move around. I intentionally avoided unmovable pages in this test to see how much latency we incur when hugepage allocations hit direct compaction. 1. Kernel hugepage allocation latencies With the system in such a fragmented state, a kernel driver then allocates as many hugepages as possible and measures allocation latency: (all latency values are in microseconds) - With vanilla 5.6.0-rc3 percentile latency –––––––––– ––––––– 5 7894 10 9496 25 12561 30 15295 40 18244 50 21229 60 27556 75 30147 80 31047 90 32859 95 33799 Total 2M hugepages allocated = 383859 (749G worth of hugepages out of 762G total free => 98% of free memory could be allocated as hugepages) - With 5.6.0-rc3 + this patch, with proactiveness=20 sysctl -w vm.compaction_proactiveness=20 percentile latency –––––––––– ––––––– 5 2 10 2 25 3 30 3 40 3 50 4 60 4 75 4 80 4 90 5 95 429 Total 2M hugepages allocated = 384105 (750G worth of hugepages out of 762G total free => 98% of free memory could be allocated as hugepages) 2. JAVA heap allocation In this test, we first fragment memory using the same method as for (1). Then, we start a Java process with a heap size set to 700G and request the heap to be allocated with THP hugepages. We also set THP to madvise to allow hugepage backing of this heap. /usr/bin/time java -Xms700G -Xmx700G -XX:+UseTransparentHugePages -XX:+AlwaysPreTouch The above command allocates 700G of Java heap using hugepages. - With vanilla 5.6.0-rc3 17.39user 1666.48system 27:37.89elapsed - With 5.6.0-rc3 + this patch, with proactiveness=20 8.35user 194.58system 3:19.62elapsed Elapsed time remains around 3:15, as proactiveness is further increased. Note that proactive compaction happens throughout the runtime of these workloads. The situation of one-time compaction, sufficient to supply hugepages for following allocation stream, can probably happen for more extreme proactiveness values, like 80 or 90. In the above Java workload, proactiveness is set to 20. The test starts with a node's score of 80 or higher, depending on the delay between the fragmentation step and starting the benchmark, which gives more-or-less time for the initial round of compaction. As t he benchmark consumes hugepages, node's score quickly rises above the high threshold (90) and proactive compaction starts again, which brings down the score to the low threshold level (80). Repeat. bpftrace also confirms proactive compaction running 20+ times during the runtime of this Java benchmark. kcompactd threads consume 100% of one of the CPUs while it tries to bring a node's score within thresholds. Backoff behavior ================ Above workloads produce a memory state which is easy to compact. However, if memory is filled with unmovable pages, proactive compaction should essentially back off. To test this aspect: - Created a kernel driver that allocates almost all memory as hugepages followed by freeing first 3/4 of each hugepage. - Set proactiveness=40 - Note that proactive_compact_node() is deferred maximum number of times with HPAGE_FRAG_CHECK_INTERVAL_MSEC of wait between each check (=> ~30 seconds between retries). [1] https://patchwork.kernel.org/patch/11098289/ [2] https://lore.kernel.org/linux-mm/20161230131412.GI13301@dhcp22.suse.cz/ [3] https://lwn.net/Articles/817905/ Signed-off-by: Nitin Gupta Signed-off-by: Andrew Morton Tested-by: Oleksandr Natalenko Reviewed-by: Vlastimil Babka Reviewed-by: Khalid Aziz Reviewed-by: Oleksandr Natalenko Cc: Vlastimil Babka Cc: Khalid Aziz Cc: Michal Hocko Cc: Mel Gorman Cc: Matthew Wilcox Cc: Mike Kravetz Cc: Joonsoo Kim Cc: David Rientjes Cc: Nitin Gupta Cc: Oleksandr Natalenko Link: http://lkml.kernel.org/r/20200616204527.19185-1-nigupta@nvidia.com Signed-off-by: Linus Torvalds

mm/workingset: prepare the workingset detection infrastructure for anon LRU

2020-08-12T17:57:55+00:00

To prepare the workingset detection for anon LRU, this patch splits workingset event counters for refault, activate and restore into anon and file variants, as well as the refaults counter in struct lruvec. Signed-off-by: Joonsoo Kim Signed-off-by: Andrew Morton Acked-by: Johannes Weiner Acked-by: Vlastimil Babka Cc: Hugh Dickins Cc: Matthew Wilcox Cc: Mel Gorman Cc: Michal Hocko Cc: Minchan Kim Link: http://lkml.kernel.org/r/1595490560-15117-4-git-send-email-iamjoonsoo.kim@lge.com Signed-off-by: Linus Torvalds

mm: memcontrol: account kernel stack per node

2020-08-07T18:33:25+00:00

Currently the kernel stack is being accounted per-zone. There is no need to do that. In addition due to being per-zone, memcg has to keep a separate MEMCG_KERNEL_STACK_KB. Make the stat per-node and deprecate MEMCG_KERNEL_STACK_KB as memcg_stat_item is an extension of node_stat_item. In addition localize the kernel stack stats updates to account_kernel_stack(). Signed-off-by: Shakeel Butt Signed-off-by: Andrew Morton Reviewed-by: Roman Gushchin Cc: Johannes Weiner Cc: Michal Hocko Link: http://lkml.kernel.org/r/20200630161539.1759185-1-shakeelb@google.com Signed-off-by: Linus Torvalds