- 01 Dec, 2019 40 commits
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Johannes Weiner authored
We use refault information to determine whether the cache workingset is stable or transitioning, and dynamically adjust the inactive:active file LRU ratio so as to maximize protection from one-off cache during stable periods, and minimize IO during transitions. With cgroups and their nested LRU lists, we currently don't do this correctly. While recursive cgroup reclaim establishes a relative LRU order among the pages of all involved cgroups, refaults only affect the local LRU order in the cgroup in which they are occuring. As a result, cache transitions can take longer in a cgrouped system as the active pages of sibling cgroups aren't challenged when they should be. [ Right now, this is somewhat theoretical, because the siblings, under continued regular reclaim pressure, should eventually run out of inactive pages - and since inactive:active *size* balancing is also done on a cgroup-local level, we will challenge the active pages eventually in most cases. But the next patch will move that relative size enforcement to the reclaim root as well, and then this patch here will be necessary to propagate refault pressure to siblings. ] This patch moves refault detection to the root of reclaim. Instead of remembering the cgroup owner of an evicted page, remember the cgroup that caused the reclaim to happen. When refaults later occur, they'll correctly influence the cross-cgroup LRU order that reclaim follows. I.e. if global reclaim kicked out pages in some subgroup A/B/C, the refault of those pages will challenge the global LRU order, and not just the local order down inside C. [hannes@cmpxchg.org: use page_memcg() instead of another lookup] Link: http://lkml.kernel.org/r/20191115160722.GA309754@cmpxchg.org Link: http://lkml.kernel.org/r/20191107205334.158354-3-hannes@cmpxchg.orgSigned-off-by:
Johannes Weiner <hannes@cmpxchg.org> Reviewed-by:
Suren Baghdasaryan <surenb@google.com> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Rik van Riel <riel@surriel.com> Cc: Shakeel Butt <shakeelb@google.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Johannes Weiner authored
Patch series "mm: fix page aging across multiple cgroups". When applications are put into unconfigured cgroups for memory accounting purposes, the cgrouping itself should not change the behavior of the page reclaim code. We expect the VM to reclaim the coldest pages in the system. But right now the VM can reclaim hot pages in one cgroup while there is eligible cold cache in others. This is because one part of the reclaim algorithm isn't truly cgroup hierarchy aware: the inactive/active list balancing. That is the part that is supposed to protect hot cache data from one-off streaming IO. The recursive cgroup reclaim scheme will scan and rotate the physical LRU lists of each eligible cgroup at the same rate in a round-robin fashion, thereby establishing a relative order among the pages of all those cgroups. However, the inactive/active balancing decisions are made locally within each cgroup, so when a cgroup is running low on cold pages, its hot pages will get reclaimed - even when sibling cgroups have plenty of cold cache eligible in the same reclaim run. For example: [root@ham ~]# head -n1 /proc/meminfo MemTotal: 1016336 kB [root@ham ~]# ./reclaimtest2.sh Establishing 50M active files in cgroup A... Hot pages cached: 12800/12800 workingset-a Linearly scanning through 18G of file data in cgroup B: real 0m4.269s user 0m0.051s sys 0m4.182s Hot pages cached: 134/12800 workingset-a The streaming IO in B, which doesn't benefit from caching at all, pushes out most of the workingset in A. Solution This series fixes the problem by elevating inactive/active balancing decisions to the toplevel of the reclaim run. This is either a cgroup that hit its limit, or straight-up global reclaim if there is physical memory pressure. From there, it takes a recursive view of the cgroup subtree to decide whether page deactivation is necessary. In the test above, the VM will then recognize that cgroup B has plenty of eligible cold cache, and that the hot pages in A can be spared: [root@ham ~]# ./reclaimtest2.sh Establishing 50M active files in cgroup A... Hot pages cached: 12800/12800 workingset-a Linearly scanning through 18G of file data in cgroup B: real 0m4.244s user 0m0.064s sys 0m4.177s Hot pages cached: 12800/12800 workingset-a Implementation Whether active pages can be deactivated or not is influenced by two factors: the inactive list dropping below a minimum size relative to the active list, and the occurence of refaults. This patch series first moves refault detection to the reclaim root, then enforces the minimum inactive size based on a recursive view of the cgroup tree's LRUs. History Note that this actually never worked correctly in Linux cgroups. In the past it worked for global reclaim and leaf limit reclaim only (we used to have two physical LRU linkages per page), but it never worked for intermediate limit reclaim over multiple leaf cgroups. We're noticing this now because 1) we're putting everything into cgroups for accounting, not just the things we want to control and 2) we're moving away from leaf limits that invoke reclaim on individual cgroups, toward large tree reclaim, triggered by high-level limits, or physical memory pressure that is influenced by local protections such as memory.low and memory.min instead. This patch (of 3): When file pages are lower than the watermark on a node, we try to force scan anonymous pages to counter-act the balancing algorithms preference for new file pages when they are likely thrashing. This is a node-level decision, but it's currently made each time we look at an lruvec. This is unnecessarily expensive and also a layering violation that makes the code harder to understand. Clean this up by making the check once per node and setting a flag in the scan_control. Link: http://lkml.kernel.org/r/20191107205334.158354-2-hannes@cmpxchg.orgSigned-off-by:
Shakeel Butt <shakeelb@google.com> Reviewed-by:
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Johannes Weiner authored
The current writeback congestion tracking has separate flags for kswapd reclaim (node level) and cgroup limit reclaim (memcg-node level). This is unnecessarily complicated: the lruvec is an existing abstraction layer for that node-memcg intersection. Introduce lruvec->flags and LRUVEC_CONGESTED. Then track that at the reclaim root level, which is either the NUMA node for global reclaim, or the cgroup-node intersection for cgroup reclaim. Link: http://lkml.kernel.org/r/20191022144803.302233-9-hannes@cmpxchg.orgSigned-off-by:
Roman Gushchin <guro@fb.com> Reviewed-by:
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Johannes Weiner authored
This function is getting long and unwieldy, split out the memcg bits. The updated shrink_node() handles the generic (node) reclaim aspects: - global vmpressure notifications - writeback and congestion throttling - reclaim/compaction management - kswapd giving up on unreclaimable nodes It then calls a new shrink_node_memcgs() which handles cgroup specifics: - the cgroup tree traversal - memory.low considerations - per-cgroup slab shrinking callbacks - per-cgroup vmpressure notifications [hannes@cmpxchg.org: rename "root" to "target_memcg", per Roman] Link: http://lkml.kernel.org/r/20191025143640.GA386981@cmpxchg.org Link: http://lkml.kernel.org/r/20191022144803.302233-8-hannes@cmpxchg.orgSigned-off-by:
Michal Hocko <mhocko@suse.com> Signed-off-by:
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Johannes Weiner authored
An lruvec holds LRU pages owned by a certain NUMA node and cgroup. Instead of awkwardly passing around a combination of a pgdat and a memcg pointer, pass down the lruvec as soon as we can look it up. Nested callers that need to access node or cgroup properties can look them them up if necessary, but there are only a few cases. Link: http://lkml.kernel.org/r/20191022144803.302233-7-hannes@cmpxchg.orgSigned-off-by:
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Johannes Weiner authored
Most of the function body is inside a loop, which imposes an additional indentation and scoping level that makes the code a bit hard to follow and modify. The looping only happens in case of reclaim-compaction, which isn't the common case. So rather than adding yet another function level to the reclaim path and have every reclaim invocation go through a level that only exists for one specific cornercase, use a retry goto. Link: http://lkml.kernel.org/r/20191022144803.302233-6-hannes@cmpxchg.orgSigned-off-by:
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Johannes Weiner authored
Seven years after introducing the global_reclaim() function, I still have to double take when reading a callsite. I don't know how others do it, this is a terrible name. Invert the meaning and rename it to cgroup_reclaim(). [ After all, "global reclaim" is just regular reclaim invoked from the page allocator. It's reclaim on behalf of a cgroup limit that is a special case of reclaim, and should be explicit - not the reverse. ] sane_reclaim() isn't very descriptive either: it tests whether we can use the regular writeback throttling - available during regular page reclaim or cgroup2 limit reclaim - or need to use the broken wait_on_page_writeback() method. Use "writeback_throttling_sane()". Link: http://lkml.kernel.org/r/20191022144803.302233-5-hannes@cmpxchg.orgSigned-off-by:
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Johannes Weiner authored
inactive_list_is_low() should be about one thing: checking the ratio between inactive and active list. Kitchensink checks like the one for swap space makes the function hard to use and modify its callsites. Luckly, most callers already have an understanding of the swap situation, so it's easy to clean up. get_scan_count() has its own, memcg-aware swap check, and doesn't even get to the inactive_list_is_low() check on the anon list when there is no swap space available. shrink_list() is called on the results of get_scan_count(), so that check is redundant too. age_active_anon() has its own totalswap_pages check right before it checks the list proportions. The shrink_node_memcg() site is the only one that doesn't do its own swap check. Add it there. Then delete the swap check from inactive_list_is_low(). Link: http://lkml.kernel.org/r/20191022144803.302233-4-hannes@cmpxchg.orgSigned-off-by:
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Johannes Weiner authored
There is a per-memcg lruvec and a NUMA node lruvec. Which one is being used is somewhat confusing right now, and it's easy to make mistakes - especially when it comes to global reclaim. How it works: when memory cgroups are enabled, we always use the root_mem_cgroup's per-node lruvecs. When memory cgroups are not compiled in or disabled at runtime, we use pgdat->lruvec. Document that in a comment. Due to the way the reclaim code is generalized, all lookups use the mem_cgroup_lruvec() helper function, and nobody should have to find the right lruvec manually right now. But to avoid future mistakes, rename the pgdat->lruvec member to pgdat->__lruvec and delete the convenience wrapper that suggests it's a commonly accessed member. While in this area, swap the mem_cgroup_lruvec() argument order. The name suggests a memcg operation, yet it takes a pgdat first and a memcg second. I have to double take every time I call this. Fix that. Link: http://lkml.kernel.org/r/20191022144803.302233-3-hannes@cmpxchg.orgSigned-off-by:
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Johannes Weiner authored
Patch series "mm: vmscan: cgroup-related cleanups". Here are 8 patches that clean up the reclaim code's interaction with cgroups a bit. They're not supposed to change any behavior, just make the implementation easier to understand and work with. This patch (of 8): This function currently takes the node or lruvec size and subtracts the zones that are excluded by the classzone index of the allocation. It uses four different types of counters to do this. Just add up the eligible zones. [cai@lca.pw: fix an undefined behavior for zone id] Link: http://lkml.kernel.org/r/20191108204407.1435-1-cai@lca.pw [akpm@linux-foundation.org: deal with the MAX_NR_ZONES special case. per Qian Cai] Link: http://lkml.kernel.org/r/64E60F6F-7582-427B-8DD5-EF97B1656F5A@lca.pw Link: http://lkml.kernel.org/r/20191022144803.302233-2-hannes@cmpxchg.orgSigned-off-by:
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Yang Shi authored
Since lumpy reclaim was removed in v3.5 scan_control is not used by may_write_to_{queue|inode} and pageout() anymore, remove the unused parameter. Link: http://lkml.kernel.org/r/1570124498-19300-1-git-send-email-yang.shi@linux.alibaba.comSigned-off-by:Yang Shi <yang.shi@linux.alibaba.com> Acked-by:
David Rientjes <rientjes@google.com> Acked-by:
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Andrey Ryabinin authored
Since 9092c71b ("mm: use sc->priority for slab shrink targets") the argument 'unsigned long *lru_pages' passed around with no purpose. Remove it. Link: http://lkml.kernel.org/r/20190228083329.31892-4-aryabinin@virtuozzo.comSigned-off-by:
Andrey Ryabinin <aryabinin@virtuozzo.com> Acked-by:
Vlastimil Babka <vbabka@suse.cz> Acked-by:
Mel Gorman <mgorman@techsingularity.net> Cc: Michal Hocko <mhocko@kernel.org> Cc: Rik van Riel <riel@surriel.com> Cc: William Kucharski <william.kucharski@oracle.com> Cc: John Hubbard <jhubbard@nvidia.com> Signed-off-by:
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lijiazi authored
Print nr_reserved_highatomic in show_free_areas, because when alloc_harder is false, this value will be subtracted from the free_pages in __zone_watermark_ok. Printing this value can help analyze memory allocaction failure issues. Link: http://lkml.kernel.org/r/19515f3de2fb6abe66b52e03e4b676a21e82beda.1573634806.git.lijiazi@xiaomi.comSigned-off-by:
lijiazi <lijiazi@xiaomi.com> Reviewed-by:
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Hao Lee authored
Both file-backed pages and anonymous pages can be unmapped. ISOLATE_UNMAPPED is not just for file-backed pages. Link: http://lkml.kernel.org/r/20191024151621.GA20400@haolee.github.ioSigned-off-by:
Hao Lee <haolee.swjtu@gmail.com> Reviewed-by:
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Mel Gorman authored
Memory hotplug needs to be able to reset and reinit the pcpu allocator batch and high limits but this action is internal to the VM. Move the declaration to internal.h Link: http://lkml.kernel.org/r/20191021094808.28824-4-mgorman@techsingularity.netSigned-off-by:
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Mel Gorman authored
Both the percpu_pagelist_fraction sysctl handler and memory hotplug have a common requirement of updating the pcpu page allocation batch and high values. Split the relevant helper to share common code. No functional change. Link: http://lkml.kernel.org/r/20191021094808.28824-3-mgorman@techsingularity.netSigned-off-by:
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Anshuman Khandual authored
HugeTLB helper alloc_gigantic_page() implements fairly generic allocation method where it scans over various zones looking for a large contiguous pfn range before trying to allocate it with alloc_contig_range(). Other than deriving the requested order from 'struct hstate', there is nothing HugeTLB specific in there. This can be made available for general use to allocate contiguous memory which could not have been allocated through the buddy allocator. alloc_gigantic_page() has been split carving out actual allocation method which is then made available via new alloc_contig_pages() helper wrapped under CONFIG_CONTIG_ALLOC. All references to 'gigantic' have been replaced with more generic term 'contig'. Allocated pages here should be freed with free_contig_range() or by calling __free_page() on each allocated page. Link: http://lkml.kernel.org/r/1571300646-32240-1-git-send-email-anshuman.khandual@arm.comSigned-off-by:
Anshuman Khandual <anshuman.khandual@arm.com> Acked-by:
David Hildenbrand <david@redhat.com> Acked-by:
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Daniel Axtens authored
In the case where KASAN directly allocates memory to back vmalloc space, don't map the early shadow page over it. We prepopulate pgds/p4ds for the range that would otherwise be empty. This is required to get it synced to hardware on boot, allowing the lower levels of the page tables to be filled dynamically. Link: http://lkml.kernel.org/r/20191031093909.9228-5-dja@axtens.netSigned-off-by:
Daniel Axtens <dja@axtens.net> Acked-by:
Dmitry Vyukov <dvyukov@google.com> Reviewed-by:
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Daniel Axtens authored
Supporting VMAP_STACK with KASAN_VMALLOC is straightforward: - clear the shadow region of vmapped stacks when swapping them in - tweak Kconfig to allow VMAP_STACK to be turned on with KASAN Link: http://lkml.kernel.org/r/20191031093909.9228-4-dja@axtens.netSigned-off-by:
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Daniel Axtens authored
Test kasan vmalloc support by adding a new test to the module. Link: http://lkml.kernel.org/r/20191031093909.9228-3-dja@axtens.netSigned-off-by:
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Daniel Axtens authored
Patch series "kasan: support backing vmalloc space with real shadow memory", v11. Currently, vmalloc space is backed by the early shadow page. This means that kasan is incompatible with VMAP_STACK. This series provides a mechanism to back vmalloc space with real, dynamically allocated memory. I have only wired up x86, because that's the only currently supported arch I can work with easily, but it's very easy to wire up other architectures, and it appears that there is some work-in-progress code to do this on arm64 and s390. This has been discussed before in the context of VMAP_STACK: - https://bugzilla.kernel.org/show_bug.cgi?id=202009 - https://lkml.org/lkml/2018/7/22/198 - https://lkml.org/lkml/2019/7/19/822 In terms of implementation details: Most mappings in vmalloc space are small, requiring less than a full page of shadow space. Allocating a full shadow page per mapping would therefore be wasteful. Furthermore, to ensure that different mappings use different shadow pages, mappings would have to be aligned to KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE. Instead, share backing space across multiple mappings. Allocate a backing page when a mapping in vmalloc space uses a particular page of the shadow region. This page can be shared by other vmalloc mappings later on. We hook in to the vmap infrastructure to lazily clean up unused shadow memory. Testing with test_vmalloc.sh on an x86 VM with 2 vCPUs shows that: - Turning on KASAN, inline instrumentation, without vmalloc, introuduces a 4.1x-4.2x slowdown in vmalloc operations. - Turning this on introduces the following slowdowns over KASAN: * ~1.76x slower single-threaded (test_vmalloc.sh performance) * ~2.18x slower when both cpus are performing operations simultaneously (test_vmalloc.sh sequential_test_order=1) This is unfortunate but given that this is a debug feature only, not the end of the world. The benchmarks are also a stress-test for the vmalloc subsystem: they're not indicative of an overall 2x slowdown! This patch (of 4): Hook into vmalloc and vmap, and dynamically allocate real shadow memory to back the mappings. Most mappings in vmalloc space are small, requiring less than a full page of shadow space. Allocating a full shadow page per mapping would therefore be wasteful. Furthermore, to ensure that different mappings use different shadow pages, mappings would have to be aligned to KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE. Instead, share backing space across multiple mappings. Allocate a backing page when a mapping in vmalloc space uses a particular page of the shadow region. This page can be shared by other vmalloc mappings later on. We hook in to the vmap infrastructure to lazily clean up unused shadow memory. To avoid the difficulties around swapping mappings around, this code expects that the part of the shadow region that covers the vmalloc space will not be covered by the early shadow page, but will be left unmapped. This will require changes in arch-specific code. This allows KASAN with VMAP_STACK, and may be helpful for architectures that do not have a separate module space (e.g. powerpc64, which I am currently working on). It also allows relaxing the module alignment back to PAGE_SIZE. Testing with test_vmalloc.sh on an x86 VM with 2 vCPUs shows that: - Turning on KASAN, inline instrumentation, without vmalloc, introuduces a 4.1x-4.2x slowdown in vmalloc operations. - Turning this on introduces the following slowdowns over KASAN: * ~1.76x slower single-threaded (test_vmalloc.sh performance) * ~2.18x slower when both cpus are performing operations simultaneously (test_vmalloc.sh sequential_test_order=3D1) This is unfortunate but given that this is a debug feature only, not the end of the world. The full benchmark results are: Performance No KASAN KASAN original x baseline KASAN vmalloc x baseline x KASAN fix_size_alloc_test 662004 11404956 17.23 19144610 28.92 1.68 full_fit_alloc_test 710950 12029752 16.92 13184651 18.55 1.10 long_busy_list_alloc_test 9431875 43990172 4.66 82970178 8.80 1.89 random_size_alloc_test 5033626 23061762 4.58 47158834 9.37 2.04 fix_align_alloc_test 1252514 15276910 12.20 31266116 24.96 2.05 random_size_align_alloc_te 1648501 14578321 8.84 25560052 15.51 1.75 align_shift_alloc_test 147 830 5.65 5692 38.72 6.86 pcpu_alloc_test 80732 125520 1.55 140864 1.74 1.12 Total Cycles 119240774314 763211341128 6.40 1390338696894 11.66 1.82 Sequential, 2 cpus No KASAN KASAN original x baseline KASAN vmalloc x baseline x KASAN fix_size_alloc_test 1423150 14276550 10.03 27733022 19.49 1.94 full_fit_alloc_test 1754219 14722640 8.39 15030786 8.57 1.02 long_busy_list_alloc_test 11451858 52154973 4.55 107016027 9.34 2.05 random_size_alloc_test 5989020 26735276 4.46 68885923 11.50 2.58 fix_align_alloc_test 2050976 20166900 9.83 50491675 24.62 2.50 random_size_align_alloc_te 2858229 17971700 6.29 38730225 13.55 2.16 align_shift_alloc_test 405 6428 15.87 26253 64.82 4.08 pcpu_alloc_test 127183 151464 1.19 216263 1.70 1.43 Total Cycles 54181269392 308723699764 5.70 650772566394 12.01 2.11 fix_size_alloc_test 1420404 14289308 10.06 27790035 19.56 1.94 full_fit_alloc_test 1736145 14806234 8.53 15274301 8.80 1.03 long_busy_list_alloc_test 11404638 52270785 4.58 107550254 9.43 2.06 random_size_alloc_test 6017006 26650625 4.43 68696127 11.42 2.58 fix_align_alloc_test 2045504 20280985 9.91 50414862 24.65 2.49 random_size_align_alloc_te 2845338 17931018 6.30 38510276 13.53 2.15 align_shift_alloc_test 472 3760 7.97 9656 20.46 2.57 pcpu_alloc_test 118643 132732 1.12 146504 1.23 1.10 Total Cycles 54040011688 309102805492 5.72 651325675652 12.05 2.11 [dja@axtens.net: fixups] Link: http://lkml.kernel.org/r/20191120052719.7201-1-dja@axtens.net Link: https://bugzilla.kernel.org/show_bug.cgi?id=3D202009 Link: http://lkml.kernel.org/r/20191031093909.9228-2-dja@axtens.net Signed-off-by: Mark Rutland <mark.rutland@arm.com> [shadow rework] Signed-off-by:
Mark Rutland <mark.rutland@arm.com> Acked-by:
Vasily Gorbik <gor@linux.ibm.com> Reviewed-by:
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Uladzislau Rezki (Sony) authored
With the new allocation approach introduced in the 5.2 kernel, it becomes possible to get rid of one global spinlock. By doing that we can further improve the KVA from the performance point of view. Basically we can have two independent locks, one for allocation part and another one for deallocation, because of two different entities: "free data structures" and "busy data structures". As a result, allocation/deallocation operations can still interfere between each other in case of running simultaneously on different CPUs, it means there is still dependency, but with two locks it becomes lower. Summarizing: - it reduces the high lock contention - it allows to perform operations on "free" and "busy" trees in parallel on different CPUs. Please note it does not solve scalability issue. Test results: In order to evaluate this patch, we can run "vmalloc test driver" to see how many CPU cycles it takes to complete all test cases running sequentially. All online CPUs run it so it will cause a high lock contention. HiKey 960, ARM64, 8xCPUs, big.LITTLE: <snip> sudo ./test_vmalloc.sh sequential_test_order=1 <snip> <default> [ 390.950557] All test took CPU0=457126382 cycles [ 391.046690] All test took CPU1=454763452 cycles [ 391.128586] All test took CPU2=454539334 cycles [ 391.222669] All test took CPU3=455649517 cycles [ 391.313946] All test took CPU4=388272196 cycles [ 391.410425] All test took CPU5=384036264 cycles [ 391.492219] All test took CPU6=387432964 cycles [ 391.578433] All test took CPU7=387201996 cycles <default> <patched> [ 304.721224] All test took CPU0=391521310 cycles [ 304.821219] All test took CPU1=393533002 cycles [ 304.917120] All test took CPU2=392243032 cycles [ 305.008986] All test took CPU3=392353853 cycles [ 305.108944] All test took CPU4=297630721 cycles [ 305.196406] All test took CPU5=297548736 cycles [ 305.288602] All test took CPU6=297092392 cycles [ 305.381088] All test took CPU7=297293597 cycles <patched> ~14%-23% patched variant is better. Link: http://lkml.kernel.org/r/20191022155800.20468-1-urezki@gmail.comSigned-off-by:Uladzislau Rezki (Sony) <urezki@gmail.com> Acked-by:
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Anders Roxell authored
When running test_vmalloc.sh smoke the following print out states that the fragment is missing. # ./test_vmalloc.sh: You must have the following enabled in your kernel: # CONFIG_TEST_VMALLOC=m Rework to add the fragment 'CONFIG_TEST_VMALLOC=m' to the config file. Link: http://lkml.kernel.org/r/20190916095217.19665-1-anders.roxell@linaro.org Fixes: a05ef00c ("selftests/vm: add script helper for CONFIG_TEST_VMALLOC_MODULE") Signed-off-by:
Anders Roxell <anders.roxell@linaro.org> Cc: Shuah Khan <shuah@kernel.org> Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com> Signed-off-by:
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Uladzislau Rezki (Sony) authored
When fit type is NE_FIT_TYPE there is a need in one extra object. Usually the "ne_fit_preload_node" per-CPU variable has it and there is no need in GFP_NOWAIT allocation, but there are exceptions. This commit just adds more explanations, as a result giving answers on questions like when it can occur, how often, under which conditions and what happens if GFP_NOWAIT gets failed. Link: http://lkml.kernel.org/r/20191016095438.12391-3-urezki@gmail.comSigned-off-by:
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Uladzislau Rezki (Sony) authored
Allocation functions should comply with the given gfp_mask as much as possible. The preallocation code in alloc_vmap_area doesn't follow that pattern and it is using a hardcoded GFP_KERNEL. Although this doesn't really make much difference because vmalloc is not GFP_NOWAIT compliant in general (e.g. page table allocations are GFP_KERNEL) there is no reason to spread that bad habit and it is good to fix the antipattern. [mhocko@suse.com: rewrite changelog] Link: http://lkml.kernel.org/r/20191016095438.12391-2-urezki@gmail.comSigned-off-by:
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Uladzislau Rezki (Sony) authored
Some background. The preemption was disabled before to guarantee that a preloaded object is available for a CPU, it was stored for. That was achieved by combining the disabling the preemption and taking the spin lock while the ne_fit_preload_node is checked. The aim was to not allocate in atomic context when spinlock is taken later, for regular vmap allocations. But that approach conflicts with CONFIG_PREEMPT_RT philosophy. It means that calling spin_lock() with disabled preemption is forbidden in the CONFIG_PREEMPT_RT kernel. Therefore, get rid of preempt_disable() and preempt_enable() when the preload is done for splitting purpose. As a result we do not guarantee now that a CPU is preloaded, instead we minimize the case when it is not, with this change, by populating the per cpu preload pointer under the vmap_area_lock. This implies that at least each caller that has done the preallocation will not fallback to an atomic allocation later. It is possible that the preallocation would be pointless or that no preallocation is done because of the race but the data shows that this is really rare. For example i run the special test case that follows the preload pattern and path. 20 "unbind" threads run it and each does 1000000 allocations. Only 3.5 times among 1000000 a CPU was not preloaded. So it can happen but the number is negligible. [mhocko@suse.com: changelog additions] Link: http://lkml.kernel.org/r/20191016095438.12391-1-urezki@gmail.com Fixes: 82dd23e8 ("mm/vmalloc.c: preload a CPU with one object for split purpose") Signed-off-by:
Steven Rostedt (VMware) <rostedt@goodmis.org> Acked-by:
Sebastian Andrzej Siewior <bigeasy@linutronix.de> Acked-by:
Daniel Wagner <dwagner@suse.de> Acked-by:
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Liu Xiang authored
gfpflags_allow_blocking() does not care about __GFP_HIGHMEM, so highmem_mask can be removed. Link: http://lkml.kernel.org/r/1568812319-3467-1-git-send-email-liuxiang_1999@126.comSigned-off-by:
Liu Xiang <liuxiang_1999@126.com> Reviewed-by:
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Michal Hocko authored
Vincent has noticed [1] that there is something unusual with the memmap allocations going on on his platform : I noticed this because on my ARM64 platform, with 1 GiB of memory the : first [and only] section is allocated from the zeroing path while with : 2 GiB of memory the first 1 GiB section is allocated from the : non-zeroing path. The underlying problem is that although sparse_buffer_init allocates enough memory for all sections on the node sparse_buffer_alloc is not able to consume them due to mismatch in the expected allocation alignement. While sparse_buffer_init preallocation uses the PAGE_SIZE alignment the real memmap has to be aligned to section_map_size() this results in a wasted initial chunk of the preallocated memmap and unnecessary fallback allocation for a section. While we are at it also change __populate_section_memmap to align to the requested size because at least VMEMMAP has constrains to have memmap properly aligned. [1] http://lkml.kernel.org/r/20191030131122.8256-1-vincent.whitchurch@axis.com [akpm@linux-foundation.org: tweak layout, per David] Link: http://lkml.kernel.org/r/20191119092642.31799-1-mhocko@kernel.org Fixes: 35fd1eb1 ("mm/sparse: abstract sparse buffer allocations") Signed-off-by:
Vincent Whitchurch <vincent.whitchurch@axis.com> Debugged-by:
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Ilya Leoshkevich authored
Building the kernel on s390 with -Og produces the following warning: WARNING: vmlinux.o(.text+0x28dabe): Section mismatch in reference from the function populate_section_memmap() to the function .meminit.text:__populate_section_memmap() The function populate_section_memmap() references the function __meminit __populate_section_memmap(). This is often because populate_section_memmap lacks a __meminit annotation or the annotation of __populate_section_memmap is wrong. While -Og is not supported, in theory this might still happen with another compiler or on another architecture. So fix this by using the correct section annotations. [iii@linux.ibm.com: v2] Link: http://lkml.kernel.org/r/20191030151639.41486-1-iii@linux.ibm.com Link: http://lkml.kernel.org/r/20191028165549.14478-1-iii@linux.ibm.comSigned-off-by:
Ilya Leoshkevich <iii@linux.ibm.com> Acked-by:
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Vincent Whitchurch authored
sparsemem without VMEMMAP has two allocation paths to allocate the memory needed for its memmap (done in sparse_mem_map_populate()). In one allocation path (sparse_buffer_alloc() succeeds), the memory is not zeroed (since it was previously allocated with memblock_alloc_try_nid_raw()). In the other allocation path (sparse_buffer_alloc() fails and sparse_mem_map_populate() falls back to memblock_alloc_try_nid()), the memory is zeroed. AFAICS this difference does not appear to be on purpose. If the code is supposed to work with non-initialized memory (__init_single_page() takes care of zeroing the struct pages which are actually used), we should consistently not zero the memory, to avoid masking bugs. ( I noticed this because on my ARM64 platform, with 1 GiB of memory the first [and only] section is allocated from the zeroing path while with 2 GiB of memory the first 1 GiB section is allocated from the non-zeroing path. ) Michal: "the main user visible problem is a memory wastage. The overal amount of memory should be small. I wouldn't call it stable material." Link: http://lkml.kernel.org/r/20191030131122.8256-1-vincent.whitchurch@axis.comSigned-off-by:
Oscar Salvador <osalvador@suse.de> Reviewed-by:
Pavel Tatashin <pasha.tatashin@soleen.com> Signed-off-by:
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David Hildenbrand authored
Our onlining/offlining code is unnecessarily complicated. Only memory blocks added during boot can have holes (a range that is not IORESOURCE_SYSTEM_RAM). Hotplugged memory never has holes (e.g., see add_memory_resource()). All memory blocks that belong to boot memory are already online. Note that boot memory can have holes and the memmap of the holes is marked PG_reserved. However, also memory allocated early during boot is PG_reserved - basically every page of boot memory that is not given to the buddy is PG_reserved. Therefore, when we stop allowing to offline memory blocks with holes, we implicitly no longer have to deal with onlining memory blocks with holes. E.g., online_pages() will do a walk_system_ram_range(..., online_pages_range), whereby online_pages_range() will effectively only free the memory holes not falling into a hole to the buddy. The other pages (holes) are kept PG_reserved (via move_pfn_range_to_zone()->memmap_init_zone()). This allows to simplify the code. For example, we no longer have to worry about marking pages that fall into memory holes PG_reserved when onlining memory. We can stop setting pages PG_reserved completely in memmap_init_zone(). Offlining memory blocks added during boot is usually not guaranteed to work either way (unmovable data might have easily ended up on that memory during boot). So stopping to do that should not really hurt. Also, people are not even aware of a setup where onlining/offlining of memory blocks with holes used to work reliably (see [1] and [2] especially regarding the hotplug path) - I doubt it worked reliably. For the use case of offlining memory to unplug DIMMs, we should see no change. (holes on DIMMs would be weird). Please note that hardware errors (PG_hwpoison) are not memory holes and are not affected by this change when offlining. [1] https://lkml.org/lkml/2019/10/22/135 [2] https://lkml.org/lkml/2019/8/14/1365 Link: http://lkml.kernel.org/r/20191119115237.6662-1-david@redhat.comReviewed-by:
Dan Williams <dan.j.williams@intel.com> Signed-off-by:
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David Hildenbrand authored
The mem_sysfs_mutex isn't really helpful. Also, it's not really clear what the mutex protects at all. The device lists of the memory subsystem are protected separately. We don't need that mutex when looking up. creating, or removing independent devices. find_memory_block_by_id() will perform locking on its own and grab a reference of the returned device. At the time memory_dev_init() is called, we cannot have concurrent hot(un)plug operations yet - we're still fairly early during boot. We don't need any locking. The creation/removal of memory block devices should be protected on a higher level - especially using the device hotplug lock to avoid documented issues (see Documentation/core-api/memory-hotplug.rst) - or if that is reworked, using similar locking. Protecting in the context of these functions only doesn't really make sense. Especially, if we would have a situation where the same memory blocks are created/deleted at the same time, there is something horribly going wrong (imagining adding/removing a DIMM at the same time from two call paths) - after the functions succeeded something else in the callers would blow up (e.g., create_memory_block_devices() succeeded but there are no memory block devices anymore). All relevant call paths (except when adding memory early during boot via ACPI, which is now documented) hold the device hotplug lock when adding memory, and when removing memory. Let's document that instead. Add a simple safety net to create_memory_block_devices() in case we would actually remove memory blocks while adding them, so we'll never dereference a NULL pointer. Simplify memory_dev_init() now that the lock is gone. Link: http://lkml.kernel.org/r/20190925082621.4927-1-david@redhat.comSigned-off-by:
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Ben Dooks (Codethink) authored
The {set,clear}_zone_contiguous are built whatever the configuratoon so move the definitions outside the current ifdef to avoid the following compiler warnings: mm/page_alloc.c:1550:6: warning: no previous prototype for 'set_zone_contiguous' [-Wmissing-prototypes] mm/page_alloc.c:1571:6: warning: no previous prototype for 'clear_zone_contiguous' [-Wmissing-prototypes] Link: http://lkml.kernel.org/r/20191106123911.7435-1-ben.dooks@codethink.co.ukSigned-off-by:Ben Dooks (Codethink) <ben.dooks@codethink.co.uk> Acked-by:
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David Hildenbrand authored
We have two types of users of page isolation: 1. Memory offlining: Offline memory so it can be unplugged. Memory won't be touched. 2. Memory allocation: Allocate memory (e.g., alloc_contig_range()) to become the owner of the memory and make use of it. For example, in case we want to offline memory, we can ignore (skip over) PageHWPoison() pages, as the memory won't get used. We can allow to offline memory. In contrast, we don't want to allow to allocate such memory. Let's generalize the approach so we can special case other types of pages we want to skip over in case we offline memory. While at it, also pass the same flags to test_pages_isolated(). Link: http://lkml.kernel.org/r/20191021172353.3056-3-david@redhat.comSigned-off-by: -
David Hildenbrand authored
Patch series "mm: Memory offlining + page isolation cleanups", v2. This patch (of 2): We call __offline_isolated_pages() from __offline_pages() after all pages were isolated and are either free (PageBuddy()) or PageHWPoison. Nothing can stop us from offlining memory at this point. In __offline_isolated_pages() we first set all affected memory sections offline (offline_mem_sections(pfn, end_pfn)), to mark the memmap as invalid (pfn_to_online_page() will no longer succeed), and then walk over all pages to pull the free pages from the free lists (to the isolated free lists, to be precise). Note that re-onlining a memory block will result in the whole memmap getting reinitialized, overwriting any old state. We already poision the memmap when offlining is complete to find any access to stale/uninitialized memmaps. So, setting the pages PageReserved() is not helpful. The memap is marked offline and all pageblocks are isolated. As soon as offline, the memmap is stale either way. This looks like a leftover from ancient times where we initialized the memmap when adding memory and not when onlining it (the pages were set PageReserved so re-onling would work as expected). Link: http://lkml.kernel.org/r/20191021172353.3056-2-david@redhat.comSigned-off-by:
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David Hildenbrand authored
Let's drop the now unused functions. Link: http://lkml.kernel.org/r/20190909114830.662-4-david@redhat.comSigned-off-by:
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David Hildenbrand authored
Let's use the generic onlining function - which will now also take care of calling kernel_map_pages(). Link: http://lkml.kernel.org/r/20190909114830.662-3-david@redhat.comSigned-off-by:
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David Hildenbrand authored
Patch series "mm/memory_hotplug: Export generic_online_page()". Let's replace the __online_page...() functions by generic_online_page(). Hyper-V only wants to delay the actual onlining of un-backed pages, so we can simpy re-use the generic function. This patch (of 3): Let's expose generic_online_page() so online_page_callback users can simply fall back to the generic implementation when actually deciding to online the pages. Link: http://lkml.kernel.org/r/20190909114830.662-2-david@redhat.comSigned-off-by:
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Alastair D'Silva authored
On PowerPC, the address ranges allocated to OpenCAPI LPC memory are allocated from firmware. These address ranges may be higher than what older kernels permit, as we increased the maximum permissable address in commit 4ffe713b ("powerpc/mm: Increase the max addressable memory to 2PB"). It is possible that the addressable range may change again in the future. In this scenario, we end up with a bogus section returned from __section_nr (see the discussion on the thread "mm: Trigger bug on if a section is not found in __section_nr"). Adding a check here means that we fail early and have an opportunity to handle the error gracefully, rather than rumbling on and potentially accessing an incorrect section. Further discussion is also on the thread ("powerpc: Perform a bounds check in arch_add_memory") http://lkml.kernel.org/r/20190827052047.31547-1-alastair@au1.ibm.com Link: http://lkml.kernel.org/r/20191001004617.7536-2-alastair@au1.ibm.comSigned-off-by:
Alastair D'Silva <alastair@d-silva.org> Reviewed-by:
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Anshuman Khandual authored
Currently during memory hot add procedure, memory gets into memblock before calling arch_add_memory() which creates its linear mapping. add_memory_resource() { .................. memblock_add_node() .................. arch_add_memory() .................. } But during memory hot remove procedure, removal from memblock happens first before its linear mapping gets teared down with arch_remove_memory() which is not consistent. Resource removal should happen in reverse order as they were added. However this does not pose any problem for now, unless there is an assumption regarding linear mapping. One example was a subtle failure on arm64 platform [1]. Though this has now found a different solution. try_remove_memory() { .................. memblock_free() memblock_remove() .................. arch_remove_memory() .................. } This changes the sequence of resource removal including memblock and linear mapping tear down during memory hot remove which will now be the reverse order in which they were added during memory hot add. The changed removal order looks like the following. try_remove_memory() { .................. arch_remove_memory() .................. memblock_free() memblock_remove() .................. } [1] https://patchwork.kernel.org/patch/11127623/ Memory hot remove now works on arm64 without this because a recent commit 60bb462fc7ad ("drivers/base/node.c: simplify unregister_memory_block_under_nodes()"). This does not fix a serious problem. It just removes an inconsistency while freeing resources during memory hot remove which for now does not pose a real problem. David mentioned that re-ordering should still make sense for consistency purpose (removing stuff in the reverse order they were added). This patch is now detached from arm64 hot-remove series. Michal: : I would just a note that the inconsistency doesn't pose any problem now : but if somebody makes any assumptions about linear mappings then it could : get subtly broken like your example for arm64 which has found a different : solution in the meantime. Link: http://lkml.kernel.org/r/1569380273-7708-1-git-send-email-anshuman.khandual@arm.comSigned-off-by:
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