kernel.git/include/linux/memcontrol.h, branch linux-5.6.y

mm, memcg: fix inconsistent oom event behavior

2020-05-20T06:22:22Z

[ Upstream commit 04fd61a4e01028210a91f0efc408c8bc61a3018c ] A recent commit 9852ae3fe529 ("mm, memcg: consider subtrees in memory.events") changed the behavior of memcg events, which will now consider subtrees in memory.events. But oom_kill event is a special one as it is used in both cgroup1 and cgroup2. In cgroup1, it is displayed in memory.oom_control. The file memory.oom_control is in both root memcg and non root memcg, that is different with memory.event as it only in non-root memcg. That commit is okay for cgroup2, but it is not okay for cgroup1 as it will cause inconsistent behavior between root memcg and non-root memcg. Here's an example on why this behavior is inconsistent in cgroup1. root memcg / memcg foo / memcg bar Suppose there's an oom_kill in memcg bar, then the oon_kill will be root memcg : memory.oom_control(oom_kill) 0 / memcg foo : memory.oom_control(oom_kill) 1 / memcg bar : memory.oom_control(oom_kill) 1 For the non-root memcg, its memory.oom_control(oom_kill) includes its descendants' oom_kill, but for root memcg, it doesn't include its descendants' oom_kill. That means, memory.oom_control(oom_kill) has different meanings in different memcgs. That is inconsistent. Then the user has to know whether the memcg is root or not. If we can't fully support it in cgroup1, for example by adding memory.events.local into cgroup1 as well, then let's don't touch its original behavior. Fixes: 9852ae3fe529 ("mm, memcg: consider subtrees in memory.events") Reported-by: Randy Dunlap Signed-off-by: Yafang Shao Signed-off-by: Andrew Morton Reviewed-by: Shakeel Butt Acked-by: Johannes Weiner Acked-by: Chris Down Acked-by: Michal Hocko Cc: Link: http://lkml.kernel.org/r/20200502141055.7378-1-laoar.shao@gmail.com Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin

mm: fork: fix kernel_stack memcg stats for various stack implementations

2020-03-29T16:47:05Z

Depending on CONFIG_VMAP_STACK and the THREAD_SIZE / PAGE_SIZE ratio the space for task stacks can be allocated using __vmalloc_node_range(), alloc_pages_node() and kmem_cache_alloc_node(). In the first and the second cases page->mem_cgroup pointer is set, but in the third it's not: memcg membership of a slab page should be determined using the memcg_from_slab_page() function, which looks at page->slab_cache->memcg_params.memcg . In this case, using mod_memcg_page_state() (as in account_kernel_stack()) is incorrect: page->mem_cgroup pointer is NULL even for pages charged to a non-root memory cgroup. It can lead to kernel_stack per-memcg counters permanently showing 0 on some architectures (depending on the configuration). In order to fix it, let's introduce a mod_memcg_obj_state() helper, which takes a pointer to a kernel object as a first argument, uses mem_cgroup_from_obj() to get a RCU-protected memcg pointer and calls mod_memcg_state(). It allows to handle all possible configurations (CONFIG_VMAP_STACK and various THREAD_SIZE/PAGE_SIZE values) without spilling any memcg/kmem specifics into fork.c . Note: This is a special version of the patch created for stable backports. It contains code from the following two patches: - mm: memcg/slab: introduce mem_cgroup_from_obj() - mm: fork: fix kernel_stack memcg stats for various stack implementations [guro@fb.com: introduce mem_cgroup_from_obj()] Link: http://lkml.kernel.org/r/20200324004221.GA36662@carbon.dhcp.thefacebook.com Fixes: 4d96ba353075 ("mm: memcg/slab: stop setting page->mem_cgroup pointer for slab pages") Signed-off-by: Roman Gushchin Signed-off-by: Andrew Morton Reviewed-by: Shakeel Butt Acked-by: Johannes Weiner Cc: Michal Hocko Cc: Bharata B Rao Cc: Shakeel Butt Cc: Link: http://lkml.kernel.org/r/20200303233550.251375-1-guro@fb.com Signed-off-by: Linus Torvalds

mm: vmscan: detect file thrashing at the reclaim root

2019-12-01T20:59:07Z

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.org Signed-off-by: Johannes Weiner Reviewed-by: Suren Baghdasaryan Cc: Andrey Ryabinin Cc: Michal Hocko Cc: Rik van Riel Cc: Shakeel Butt Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: vmscan: harmonize writeback congestion tracking for nodes & memcgs

2019-12-01T20:59:07Z

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.org Signed-off-by: Johannes Weiner Reviewed-by: Roman Gushchin Reviewed-by: Shakeel Butt Cc: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: clean up and clarify lruvec lookup procedure

2019-12-01T20:59:06Z

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.org Signed-off-by: Johannes Weiner Acked-by: Michal Hocko Reviewed-by: Shakeel Butt Cc: Roman Gushchin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: vmscan: memcontrol: remove mem_cgroup_select_victim_node()

2019-12-01T14:29:18Z

Since commit 1ba6fc9af35b ("mm: vmscan: do not share cgroup iteration between reclaimers"), the memcg reclaim does not bail out earlier based on sc->nr_reclaimed and will traverse all the nodes. All the reclaimable pages of the memcg on all the nodes will be scanned relative to the reclaim priority. So, there is no need to maintain state regarding which node to start the memcg reclaim from. This patch effectively reverts the commit 889976dbcb12 ("memcg: reclaim memory from nodes in round-robin order") and commit 453a9bf347f1 ("memcg: fix numa scan information update to be triggered by memory event"). [shakeelb@google.com: v2] Link: http://lkml.kernel.org/r/20191030204232.139424-1-shakeelb@google.com Link: http://lkml.kernel.org/r/20191029234753.224143-1-shakeelb@google.com Signed-off-by: Shakeel Butt Acked-by: Roman Gushchin Acked-by: Michal Hocko Acked-by: Johannes Weiner Cc: Greg Thelen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

include/linux/memcontrol.h: fix comments based on per-node memcg

2019-12-01T14:29:18Z

These comments should be updated as memcg limit enforcement has been moved from zones to nodes. Link: http://lkml.kernel.org/r/20191022150618.GA15519@haolee.github.io Signed-off-by: Hao Lee Acked-by: Roman Gushchin Acked-by: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, memcg: clean up reclaim iter array

2019-12-01T14:29:18Z

The mem_cgroup_reclaim_cookie is only used in memcg softlimit reclaim now, and the priority of the reclaim is always 0. We don't need to define the iter in struct mem_cgroup_per_node as an array any more. That could make the code more clear and save some space. Link: http://lkml.kernel.org/r/1569897728-1686-1-git-send-email-laoar.shao@gmail.com Signed-off-by: Yafang Shao Acked-by: Michal Hocko Cc: Johannes Weiner Cc: Vladimir Davydov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, memcg: make scan aggression always exclude protection

2019-10-07T22:47:20Z

This patch is an incremental improvement on the existing memory.{low,min} relative reclaim work to base its scan pressure calculations on how much protection is available compared to the current usage, rather than how much the current usage is over some protection threshold. This change doesn't change the experience for the user in the normal case too much. One benefit is that it replaces the (somewhat arbitrary) 100% cutoff with an indefinite slope, which makes it easier to ballpark a memory.low value. As well as this, the old methodology doesn't quite apply generically to machines with varying amounts of physical memory. Let's say we have a top level cgroup, workload.slice, and another top level cgroup, system-management.slice. We want to roughly give 12G to system-management.slice, so on a 32GB machine we set memory.low to 20GB in workload.slice, and on a 64GB machine we set memory.low to 52GB. However, because these are relative amounts to the total machine size, while the amount of memory we want to generally be willing to yield to system.slice is absolute (12G), we end up putting more pressure on system.slice just because we have a larger machine and a larger workload to fill it, which seems fairly unintuitive. With this new behaviour, we don't end up with this unintended side effect. Previously the way that memory.low protection works is that if you are 50% over a certain baseline, you get 50% of your normal scan pressure. This is certainly better than the previous cliff-edge behaviour, but it can be improved even further by always considering memory under the currently enforced protection threshold to be out of bounds. This means that we can set relatively low memory.low thresholds for variable or bursty workloads while still getting a reasonable level of protection, whereas with the previous version we may still trivially hit the 100% clamp. The previous 100% clamp is also somewhat arbitrary, whereas this one is more concretely based on the currently enforced protection threshold, which is likely easier to reason about. There is also a subtle issue with the way that proportional reclaim worked previously -- it promotes having no memory.low, since it makes pressure higher during low reclaim. This happens because we base our scan pressure modulation on how far memory.current is between memory.min and memory.low, but if memory.low is unset, we only use the overage method. In most cromulent configurations, this then means that we end up with *more* pressure than with no memory.low at all when we're in low reclaim, which is not really very usable or expected. With this patch, memory.low and memory.min affect reclaim pressure in a more understandable and composable way. For example, from a user standpoint, "protected" memory now remains untouchable from a reclaim aggression standpoint, and users can also have more confidence that bursty workloads will still receive some amount of guaranteed protection. Link: http://lkml.kernel.org/r/20190322160307.GA3316@chrisdown.name Signed-off-by: Chris Down Reviewed-by: Roman Gushchin Acked-by: Johannes Weiner Acked-by: Michal Hocko Cc: Tejun Heo Cc: Dennis Zhou Cc: Vladimir Davydov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, memcg: make memory.emin the baseline for utilisation determination

2019-10-07T22:47:20Z

Roman points out that when when we do the low reclaim pass, we scale the reclaim pressure relative to position between 0 and the maximum protection threshold. However, if the maximum protection is based on memory.elow, and memory.emin is above zero, this means we still may get binary behaviour on second-pass low reclaim. This is because we scale starting at 0, not starting at memory.emin, and since we don't scan at all below emin, we end up with cliff behaviour. This should be a fairly uncommon case since usually we don't go into the second pass, but it makes sense to scale our low reclaim pressure starting at emin. You can test this by catting two large sparse files, one in a cgroup with emin set to some moderate size compared to physical RAM, and another cgroup without any emin. In both cgroups, set an elow larger than 50% of physical RAM. The one with emin will have less page scanning, as reclaim pressure is lower. Rebase on top of and apply the same idea as what was applied to handle cgroup_memory=disable properly for the original proportional patch http://lkml.kernel.org/r/20190201045711.GA18302@chrisdown.name ("mm, memcg: Handle cgroup_disable=memory when getting memcg protection"). Link: http://lkml.kernel.org/r/20190201051810.GA18895@chrisdown.name Signed-off-by: Chris Down Suggested-by: Roman Gushchin Acked-by: Johannes Weiner Cc: Michal Hocko Cc: Tejun Heo Cc: Dennis Zhou Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds