- 07 Aug, 2020 40 commits
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Alex Zhang authored
This function implicitly assumes that the addr passed in is page aligned. A non page aligned addr could ultimately cause a kernel bug in remap_pte_range as the exit condition in the logic loop may never be satisfied. This patch documents the need for the requirement, as well as explicitly adds a check for it. Signed-off-by:
Alex Zhang <zhangalex@google.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Reviewed-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Ralph Campbell authored
In zap_pte_range(), the check for non_swap_entry() and is_device_private_entry() is unnecessary since the latter is sufficient to determine if the page is a device private page. Remove the test for non_swap_entry() to simplify the code and for clarity. Signed-off-by:
Ralph Campbell <rcampbell@nvidia.com> Signed-off-by:
Jason Gunthorpe <jgg@mellanox.com> Acked-by:
David Hildenbrand <david@redhat.com> Link: http://lkml.kernel.org/r/20200615175405.4613-1-rcampbell@nvidia.comSigned-off-by:
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Michal Koutný authored
When workload runs in cgroups that aren't directly below root cgroup and their parent specifies reclaim protection, it may end up ineffective. The reason is that propagate_protected_usage() is not called in all hierarchy up. All the protected usage is incorrectly accumulated in the workload's parent. This means that siblings_low_usage is overestimated and effective protection underestimated. Even though it is transitional phenomenon (uncharge path does correct propagation and fixes the wrong children_low_usage), it can undermine the intended protection unexpectedly. We have noticed this problem while seeing a swap out in a descendant of a protected memcg (intermediate node) while the parent was conveniently under its protection limit and the memory pressure was external to that hierarchy. Michal has pinpointed this down to the wrong siblings_low_usage which led to the unwanted reclaim. The fix is simply updating children_low_usage in respective ancestors also in the charging path. Fixes: 23067153 ("mm: memory.low hierarchical behavior") Signed-off-by:
Michal Koutný <mkoutny@suse.com> Signed-off-by:
Michal Hocko <mhocko@suse.com> Signed-off-by:
Roman Gushchin <guro@fb.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Tejun Heo <tj@kernel.org> Cc: <stable@vger.kernel.org> [4.18+] Link: http://lkml.kernel.org/r/20200803153231.15477-1-mhocko@kernel.orgSigned-off-by:
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Johannes Weiner authored
When an outside process lowers one of the memory limits of a cgroup (or uses the force_empty knob in cgroup1), direct reclaim is performed in the context of the write(), in order to directly enforce the new limit and have it being met by the time the write() returns. Currently, this reclaim activity is accounted as memory pressure in the cgroup that the writer(!) belongs to. This is unexpected. It specifically causes problems for senpai (https://github.com/facebookincubator/senpai), which is an agent that routinely adjusts the memory limits and performs associated reclaim work in tens or even hundreds of cgroups running on the host. The cgroup that senpai is running in itself will report elevated levels of memory pressure, even though it itself is under no memory shortage or any sort of distress. Move the psi annotation from the central cgroup reclaim function to callsites in the allocation context, and thereby no longer count any limit-setting reclaim as memory pressure. If the newly set limit causes the workload inside the cgroup into direct reclaim, that of course will continue to count as memory pressure. Signed-off-by:
Johannes Weiner <hannes@cmpxchg.org> Signed-off-by:
Shakeel Butt <shakeelb@google.com> Reviewed-by:
Chris Down <chris@chrisdown.name> Acked-by:
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Johannes Weiner authored
Commit 8c8c383c ("mm: memcontrol: try harder to set a new memory.high") inadvertently removed a callback to recalculate the writeback cache size in light of a newly configured memory.high limit. Without letting the writeback cache know about a potentially heavily reduced limit, it may permit too many dirty pages, which can cause unnecessary reclaim latencies or even avoidable OOM situations. This was spotted while reading the code, it hasn't knowingly caused any problems in practice so far. Fixes: 8c8c383c ("mm: memcontrol: try harder to set a new memory.high") Signed-off-by:
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Yafang Shao authored
Memcg oom killer invocation is synchronized by the global oom_lock and tasks are sleeping on the lock while somebody is selecting the victim or potentially race with the oom_reaper is releasing the victim's memory. This can result in a pointless oom killer invocation because a waiter might be racing with the oom_reaper P1 oom_reaper P2 oom_reap_task mutex_lock(oom_lock) out_of_memory # no victim because we have one already __oom_reap_task_mm mute_unlock(oom_lock) mutex_lock(oom_lock) set MMF_OOM_SKIP select_bad_process # finds a new victim The page allocator prevents from this race by trying to allocate after the lock can be acquired (in __alloc_pages_may_oom) which acts as a last minute check. Moreover page allocator simply doesn't block on the oom_lock and simply retries the whole reclaim process. Memcg oom killer should do the last minute check as well. Call mem_cgroup_margin to do that. Trylock on the oom_lock could be done as well but this doesn't seem to be necessary at this stage. [mhocko@kernel.org: commit log] Suggested-by:Michal Hocko <mhocko@kernel.org> Signed-off-by:
Yafang Shao <laoar.shao@gmail.com> Signed-off-by:
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Chris Down authored
mem_cgroup_protected currently is both used to set effective low and min and return a mem_cgroup_protection based on the result. As a user, this can be a little unexpected: it appears to be a simple predicate function, if not for the big warning in the comment above about the order in which it must be executed. This change makes it so that we separate the state mutations from the actual protection checks, which makes it more obvious where we need to be careful mutating internal state, and where we are simply checking and don't need to worry about that. [mhocko@suse.com - don't check protection on root memcgs] Suggested-by:
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Yafang Shao authored
Patch series "mm, memcg: memory.{low,min} reclaim fix & cleanup", v4. This series contains a fix for a edge case in my earlier protection calculation patches, and a patch to make the area overall a little more robust to hopefully help avoid this in future. This patch (of 2): A cgroup can have both memory protection and a memory limit to isolate it from its siblings in both directions - for example, to prevent it from being shrunk below 2G under high pressure from outside, but also from growing beyond 4G under low pressure. Commit 9783aa99 ("mm, memcg: proportional memory.{low,min} reclaim") implemented proportional scan pressure so that multiple siblings in excess of their protection settings don't get reclaimed equally but instead in accordance to their unprotected portion. During limit reclaim, this proportionality shouldn't apply of course: there is no competition, all pressure is from within the cgroup and should be applied as such. Reclaim should operate at full efficiency. However, mem_cgroup_protected() never expected anybody to look at the effective protection values when it indicated that the cgroup is above its protection. As a result, a query during limit reclaim may return stale protection values that were calculated by a previous reclaim cycle in which the cgroup did have siblings. When this happens, reclaim is unnecessarily hesitant and potentially slow to meet the desired limit. In theory this could lead to premature OOM kills, although it's not obvious this has occurred in practice. Workaround the problem by special casing reclaim roots in mem_cgroup_protection. These memcgs are never participating in the reclaim protection because the reclaim is internal. We have to ignore effective protection values for reclaim roots because mem_cgroup_protected might be called from racing reclaim contexts with different roots. Calculation is relying on root -> leaf tree traversal therefore top-down reclaim protection invariants should hold. The only exception is the reclaim root which should have effective protection set to 0 but that would be problematic for the following setup: Let's have global and A's reclaim in parallel: | A (low=2G, usage = 3G, max = 3G, children_low_usage = 1.5G) |\ | C (low = 1G, usage = 2.5G) B (low = 1G, usage = 0.5G) for A reclaim we have B.elow = B.low C.elow = C.low For the global reclaim A.elow = A.low B.elow = min(B.usage, B.low) because children_low_usage <= A.elow C.elow = min(C.usage, C.low) With the effective values resetting we have A reclaim A.elow = 0 B.elow = B.low C.elow = C.low and global reclaim could see the above and then B.elow = C.elow = 0 because children_low_usage > A.elow Which means that protected memcgs would get reclaimed. In future we would like to make mem_cgroup_protected more robust against racing reclaim contexts but that is likely more complex solution than this simple workaround. [hannes@cmpxchg.org - large part of the changelog] [mhocko@suse.com - workaround explanation] [chris@chrisdown.name - retitle] Fixes: 9783aa99 ("mm, memcg: proportional memory.{low,min} reclaim") Signed-off-by: -
Chris Down authored
Reclaim retries have been set to 5 since the beginning of time in commit 66e1707b ("Memory controller: add per cgroup LRU and reclaim"). However, we now have a generally agreed-upon standard for page reclaim: MAX_RECLAIM_RETRIES (currently 16), added many years later in commit 0a0337e0 ("mm, oom: rework oom detection"). In the absence of a compelling reason to declare an OOM earlier in memcg context than page allocator context, it seems reasonable to supplant MEM_CGROUP_RECLAIM_RETRIES with MAX_RECLAIM_RETRIES, making the page allocator and memcg internals more similar in semantics when reclaim fails to produce results, avoiding premature OOMs or throttling. Signed-off-by:
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Chris Down authored
Patch series "mm, memcg: reclaim harder before high throttling", v2. This patch (of 2): In Facebook production, we've seen cases where cgroups have been put into allocator throttling even when they appear to have a lot of slack file caches which should be trivially reclaimable. Looking more closely, the problem is that we only try a single cgroup reclaim walk for each return to usermode before calculating whether or not we should throttle. This single attempt doesn't produce enough pressure to shrink for cgroups with a rapidly growing amount of file caches prior to entering allocator throttling. As an example, we see that threads in an affected cgroup are stuck in allocator throttling: # for i in $(cat cgroup.threads); do > grep over_high "/proc/$i/stack" > done [<0>] mem_cgroup_handle_over_high+0x10b/0x150 [<0>] mem_cgroup_handle_over_high+0x10b/0x150 [<0>] mem_cgroup_handle_over_high+0x10b/0x150 ...however, there is no I/O pressure reported by PSI, despite a lot of slack file pages: # cat memory.pressure some avg10=78.50 avg60=84.99 avg300=84.53 total=5702440903 full avg10=78.50 avg60=84.99 avg300=84.53 total=5702116959 # cat io.pressure some avg10=0.00 avg60=0.00 avg300=0.00 total=78051391 full avg10=0.00 avg60=0.00 avg300=0.00 total=78049640 # grep _file memory.stat inactive_file 1370939392 active_file 661635072 This patch changes the behaviour to retry reclaim either until the current task goes below the 10ms grace period, or we are making no reclaim progress at all. In the latter case, we enter reclaim throttling as before. To a user, there's no intuitive reason for the reclaim behaviour to differ from hitting memory.high as part of a new allocation, as opposed to hitting memory.high because someone lowered its value. As such this also brings an added benefit: it unifies the reclaim behaviour between the two. There's precedent for this behaviour: we already do reclaim retries when writing to memory.{high,max}, in max reclaim, and in the page allocator itself. Signed-off-by: -
Roman Gushchin authored
Memory.high limit is implemented in a way such that the kernel penalizes all threads which are allocating a memory over the limit. Forcing all threads into the synchronous reclaim and adding some artificial delays allows to slow down the memory consumption and potentially give some time for userspace oom handlers/resource control agents to react. It works nicely if the memory usage is hitting the limit from below, however it works sub-optimal if a user adjusts memory.high to a value way below the current memory usage. It basically forces all workload threads (doing any memory allocations) into the synchronous reclaim and sleep. This makes the workload completely unresponsive for a long period of time and can also lead to a system-wide contention on lru locks. It can happen even if the workload is not actually tight on memory and has, for example, a ton of cold pagecache. In the current implementation writing to memory.high causes an atomic update of page counter's high value followed by an attempt to reclaim enough memory to fit into the new limit. To fix the problem described above, all we need is to change the order of execution: try to push the memory usage under the limit first, and only then set the new high limit. Reported-by:
Domas Mituzas <domas@fb.com> Signed-off-by:
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Roman Gushchin authored
Currently memcg_kmem_enabled() is optimized for the kernel memory accounting being off. It was so for a long time, and arguably the reason behind was that the kernel memory accounting was initially an opt-in feature. However, now it's on by default on both cgroup v1 and cgroup v2, and it's on for all cgroups. So let's switch over to static_branch_likely() to reflect this fact. Unlikely there is a significant performance difference, as the cost of a memory allocation and its accounting significantly exceeds the cost of a jump. However, the conversion makes the code look more logically. Signed-off-by:
Vlastimil Babka <vbabka@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Pekka Enberg <penberg@kernel.org> Link: http://lkml.kernel.org/r/20200707173612.124425-3-guro@fb.comSigned-off-by:
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Roman Gushchin authored
charge_slab_page() and uncharge_slab_page() are not related anymore to memcg charging and uncharging. In order to make their names less confusing, let's rename them to account_slab_page() and unaccount_slab_page() respectively. Signed-off-by:
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Roman Gushchin authored
charge_slab_page() is not using the gfp argument anymore, remove it. Signed-off-by:
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Shakeel Butt authored
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:
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Roman Gushchin authored
Add a drgn-based tool to display slab information for a given memcg. Can replace cgroup v1 memory.kmem.slabinfo interface on cgroup v2, but in a more flexiable way. Currently supports only SLUB configuration, but SLAB can be trivially added later. Output example: $ sudo ./tools/cgroup/memcg_slabinfo.py /sys/fs/cgroup/user.slice/user-111017.slice/user\@111017.service shmem_inode_cache 92 92 704 46 8 : tunables 0 0 0 : slabdata 2 2 0 eventpoll_pwq 56 56 72 56 1 : tunables 0 0 0 : slabdata 1 1 0 eventpoll_epi 32 32 128 32 1 : tunables 0 0 0 : slabdata 1 1 0 kmalloc-8 0 0 8 512 1 : tunables 0 0 0 : slabdata 0 0 0 kmalloc-96 0 0 96 42 1 : tunables 0 0 0 : slabdata 0 0 0 kmalloc-2048 0 0 2048 16 8 : tunables 0 0 0 : slabdata 0 0 0 kmalloc-64 128 128 64 64 1 : tunables 0 0 0 : slabdata 2 2 0 mm_struct 160 160 1024 32 8 : tunables 0 0 0 : slabdata 5 5 0 signal_cache 96 96 1024 32 8 : tunables 0 0 0 : slabdata 3 3 0 sighand_cache 45 45 2112 15 8 : tunables 0 0 0 : slabdata 3 3 0 files_cache 138 138 704 46 8 : tunables 0 0 0 : slabdata 3 3 0 task_delay_info 153 153 80 51 1 : tunables 0 0 0 : slabdata 3 3 0 task_struct 27 27 3520 9 8 : tunables 0 0 0 : slabdata 3 3 0 radix_tree_node 56 56 584 28 4 : tunables 0 0 0 : slabdata 2 2 0 btrfs_inode 140 140 1136 28 8 : tunables 0 0 0 : slabdata 5 5 0 kmalloc-1024 64 64 1024 32 8 : tunables 0 0 0 : slabdata 2 2 0 kmalloc-192 84 84 192 42 2 : tunables 0 0 0 : slabdata 2 2 0 inode_cache 54 54 600 27 4 : tunables 0 0 0 : slabdata 2 2 0 kmalloc-128 0 0 128 32 1 : tunables 0 0 0 : slabdata 0 0 0 kmalloc-512 32 32 512 32 4 : tunables 0 0 0 : slabdata 1 1 0 skbuff_head_cache 32 32 256 32 2 : tunables 0 0 0 : slabdata 1 1 0 sock_inode_cache 46 46 704 46 8 : tunables 0 0 0 : slabdata 1 1 0 cred_jar 378 378 192 42 2 : tunables 0 0 0 : slabdata 9 9 0 proc_inode_cache 96 96 672 24 4 : tunables 0 0 0 : slabdata 4 4 0 dentry 336 336 192 42 2 : tunables 0 0 0 : slabdata 8 8 0 filp 697 864 256 32 2 : tunables 0 0 0 : slabdata 27 27 0 anon_vma 644 644 88 46 1 : tunables 0 0 0 : slabdata 14 14 0 pid 1408 1408 64 64 1 : tunables 0 0 0 : slabdata 22 22 0 vm_area_struct 1200 1200 200 40 2 : tunables 0 0 0 : slabdata 30 30 0 Signed-off-by:
Tejun Heo <tj@kernel.org> Cc: Christoph Lameter <cl@linux.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Shakeel Butt <shakeelb@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Link: http://lkml.kernel.org/r/20200623174037.3951353-20-guro@fb.comSigned-off-by:
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Roman Gushchin authored
Add some tests to cover the kernel memory accounting functionality. These are covering some issues (and changes) we had recently. 1) A test which allocates a lot of negative dentries, checks memcg slab statistics, creates memory pressure by setting memory.max to some low value and checks that some number of slabs was reclaimed. 2) A test which covers side effects of memcg destruction: it creates and destroys a large number of sub-cgroups, each containing a multi-threaded workload which allocates and releases some kernel memory. Then it checks that the charge ans memory.stats do add up on the parent level. 3) A test which reads /proc/kpagecgroup and implicitly checks that it doesn't crash the system. 4) A test which spawns a large number of threads and checks that the kernel stacks accounting works as expected. 5) A test which checks that living charged slab objects are not preventing the memory cgroup from being released after being deleted by a user. Signed-off-by:
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Roman Gushchin authored
Instead of having two sets of kmem_caches: one for system-wide and non-accounted allocations and the second one shared by all accounted allocations, we can use just one. The idea is simple: space for obj_cgroup metadata can be allocated on demand and filled only for accounted allocations. It allows to remove a bunch of code which is required to handle kmem_cache clones for accounted allocations. There is no more need to create them, accumulate statistics, propagate attributes, etc. It's a quite significant simplification. Also, because the total number of slab_caches is reduced almost twice (not all kmem_caches have a memcg clone), some additional memory savings are expected. On my devvm it additionally saves about 3.5% of slab memory. [guro@fb.com: fix build on MIPS] Link: http://lkml.kernel.org/r/20200717214810.3733082-1-guro@fb.comSuggested-by:
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Roman Gushchin authored
memcg_accumulate_slabinfo() is never called with a non-root kmem_cache as a first argument, so the is_root_cache(s) check is redundant and can be removed without any functional change. Signed-off-by:
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Roman Gushchin authored
Currently there are two lists of kmem_caches: 1) slab_caches, which contains all kmem_caches, 2) slab_root_caches, which contains only root kmem_caches. And there is some preprocessor magic to have a single list if CONFIG_MEMCG_KMEM isn't enabled. It was required earlier because the number of non-root kmem_caches was proportional to the number of memory cgroups and could reach really big values. Now, when it cannot exceed the number of root kmem_caches, there is really no reason to maintain two lists. We never iterate over the slab_root_caches list on any hot paths, so it's perfectly fine to iterate over slab_caches and filter out non-root kmem_caches. It allows to remove a lot of config-dependent code and two pointers from the kmem_cache structure. Signed-off-by:
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Roman Gushchin authored
The memcg_kmem_get_cache() function became really trivial, so let's just inline it into the single call point: memcg_slab_pre_alloc_hook(). It will make the code less bulky and can also help the compiler to generate a better code. Signed-off-by:
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Roman Gushchin authored
Because the number of non-root kmem_caches doesn't depend on the number of memory cgroups anymore and is generally not very big, there is no more need for a dedicated workqueue. Also, as there is no more need to pass any arguments to the memcg_create_kmem_cache() except the root kmem_cache, it's possible to just embed the work structure into the kmem_cache and avoid the dynamic allocation of the work structure. This will also simplify the synchronization: for each root kmem_cache there is only one work. So there will be no more concurrent attempts to create a non-root kmem_cache for a root kmem_cache: the second and all following attempts to queue the work will fail. On the kmem_cache destruction path there is no more need to call the expensive flush_workqueue() and wait for all pending works to be finished. Instead, cancel_work_sync() can be used to cancel/wait for only one work. Signed-off-by:
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Roman Gushchin authored
This is fairly big but mostly red patch, which makes all accounted slab allocations use a single set of kmem_caches instead of creating a separate set for each memory cgroup. Because the number of non-root kmem_caches is now capped by the number of root kmem_caches, there is no need to shrink or destroy them prematurely. They can be perfectly destroyed together with their root counterparts. This allows to dramatically simplify the management of non-root kmem_caches and delete a ton of code. This patch performs the following changes: 1) introduces memcg_params.memcg_cache pointer to represent the kmem_cache which will be used for all non-root allocations 2) reuses the existing memcg kmem_cache creation mechanism to create memcg kmem_cache on the first allocation attempt 3) memcg kmem_caches are named <kmemcache_name>-memcg, e.g. dentry-memcg 4) simplifies memcg_kmem_get_cache() to just return memcg kmem_cache or schedule it's creation and return the root cache 5) removes almost all non-root kmem_cache management code (separate refcounter, reparenting, shrinking, etc) 6) makes slab debugfs to display root_mem_cgroup css id and never show :dead and :deact flags in the memcg_slabinfo attribute. Following patches in the series will simplify the kmem_cache creation. Signed-off-by:
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Roman Gushchin authored
To make the memcg_kmem_bypass() function available outside of the memcontrol.c, let's move it to memcontrol.h. The function is small and nicely fits into static inline sort of functions. It will be used from the slab code. Signed-off-by:
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Roman Gushchin authored
Deprecate memory.kmem.slabinfo. An empty file will be presented if corresponding config options are enabled. The interface is implementation dependent, isn't present in cgroup v2, and is generally useful only for core mm debugging purposes. In other words, it doesn't provide any value for the absolute majority of users. A drgn-based replacement can be found in tools/cgroup/memcg_slabinfo.py. It does support cgroup v1 and v2, mimics memory.kmem.slabinfo output and also allows to get any additional information without a need to recompile the kernel. If a drgn-based solution is too slow for a task, a bpf-based tracing tool can be used, which can easily keep track of all slab allocations belonging to a memory cgroup. Signed-off-by:
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Roman Gushchin authored
Switch to per-object accounting of non-root slab objects. Charging is performed using obj_cgroup API in the pre_alloc hook. Obj_cgroup is charged with the size of the object and the size of metadata: as now it's the size of an obj_cgroup pointer. If the amount of memory has been charged successfully, the actual allocation code is executed. Otherwise, -ENOMEM is returned. In the post_alloc hook if the actual allocation succeeded, corresponding vmstats are bumped and the obj_cgroup pointer is saved. Otherwise, the charge is canceled. On the free path obj_cgroup pointer is obtained and used to uncharge the size of the releasing object. Memcg and lruvec counters are now representing only memory used by active slab objects and do not include the free space. The free space is shared and doesn't belong to any specific cgroup. Global per-node slab vmstats are still modified from (un)charge_slab_page() functions. The idea is to keep all slab pages accounted as slab pages on system level. Signed-off-by:
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Roman Gushchin authored
Store the obj_cgroup pointer in the corresponding place of page->obj_cgroups for each allocated non-root slab object. Make sure that each allocated object holds a reference to obj_cgroup. Objcg pointer is obtained from the memcg->objcg dereferencing in memcg_kmem_get_cache() and passed from pre_alloc_hook to post_alloc_hook. Then in case of successful allocation(s) it's getting stored in the page->obj_cgroups vector. The objcg obtaining part look a bit bulky now, but it will be simplified by next commits in the series. Signed-off-by:
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Roman Gushchin authored
Allocate and release memory to store obj_cgroup pointers for each non-root slab page. Reuse page->mem_cgroup pointer to store a pointer to the allocated space. This commit temporarily increases the memory footprint of the kernel memory accounting. To store obj_cgroup pointers we'll need a place for an objcg_pointer for each allocated object. However, the following patches in the series will enable sharing of slab pages between memory cgroups, which will dramatically increase the total slab utilization. And the final memory footprint will be significantly smaller than before. To distinguish between obj_cgroups and memcg pointers in case when it's not obvious which one is used (as in page_cgroup_ino()), let's always set the lowest bit in the obj_cgroup case. The original obj_cgroups pointer is marked to be ignored by kmemleak, which otherwise would report a memory leak for each allocated vector. Signed-off-by:
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Roman Gushchin authored
Obj_cgroup API provides an ability to account sub-page sized kernel objects, which potentially outlive the original memory cgroup. The top-level API consists of the following functions: bool obj_cgroup_tryget(struct obj_cgroup *objcg); void obj_cgroup_get(struct obj_cgroup *objcg); void obj_cgroup_put(struct obj_cgroup *objcg); int obj_cgroup_charge(struct obj_cgroup *objcg, gfp_t gfp, size_t size); void obj_cgroup_uncharge(struct obj_cgroup *objcg, size_t size); struct mem_cgroup *obj_cgroup_memcg(struct obj_cgroup *objcg); struct obj_cgroup *get_obj_cgroup_from_current(void); Object cgroup is basically a pointer to a memory cgroup with a per-cpu reference counter. It substitutes a memory cgroup in places where it's necessary to charge a custom amount of bytes instead of pages. All charged memory rounded down to pages is charged to the corresponding memory cgroup using __memcg_kmem_charge(). It implements reparenting: on memcg offlining it's getting reattached to the parent memory cgroup. Each online memory cgroup has an associated active object cgroup to handle new allocations and the list of all attached object cgroups. On offlining of a cgroup this list is reparented and for each object cgroup in the list the memcg pointer is swapped to the parent memory cgroup. It prevents long-living objects from pinning the original memory cgroup in the memory. The implementation is based on byte-sized per-cpu stocks. A sub-page sized leftover is stored in an atomic field, which is a part of obj_cgroup object. So on cgroup offlining the leftover is automatically reparented. memcg->objcg is rcu protected. objcg->memcg is a raw pointer, which is always pointing at a memory cgroup, but can be atomically swapped to the parent memory cgroup. So a user must ensure the lifetime of the cgroup, e.g. grab rcu_read_lock or css_set_lock. Suggested-by:
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Johannes Weiner authored
The reference counting of a memcg is currently coupled directly to how many 4k pages are charged to it. This doesn't work well with Roman's new slab controller, which maintains pools of objects and doesn't want to keep an extra balance sheet for the pages backing those objects. This unusual refcounting design (reference counts usually track pointers to an object) is only for historical reasons: memcg used to not take any css references and simply stalled offlining until all charges had been reparented and the page counters had dropped to zero. When we got rid of the reparenting requirement, the simple mechanical translation was to take a reference for every charge. More historical context can be found in commit e8ea14cc ("mm: memcontrol: take a css reference for each charged page"), commit 64f21993 ("mm: memcontrol: remove obsolete kmemcg pinning tricks") and commit b2052564 ("mm: memcontrol: continue cache reclaim from offlined groups"). The new slab controller exposes the limitations in this scheme, so let's switch it to a more idiomatic reference counting model based on actual kernel pointers to the memcg: - The per-cpu stock holds a reference to the memcg its caching - User pages hold a reference for their page->mem_cgroup. Transparent huge pages will no longer acquire tail references in advance, we'll get them if needed during the split. - Kernel pages hold a reference for their page->mem_cgroup - Pages allocated in the root cgroup will acquire and release css references for simplicity. css_get() and css_put() optimize that. - The current memcg_charge_slab() already hacked around the per-charge references; this change gets rid of that as well. - tcp accounting will handle reference in mem_cgroup_sk_{alloc,free} Roman: 1) Rebased on top of the current mm tree: added css_get() in mem_cgroup_charge(), dropped mem_cgroup_try_charge() part 2) I've reformatted commit references in the commit log to make checkpatch.pl happy. [hughd@google.com: remove css_put_many() from __mem_cgroup_clear_mc()] Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2007302011450.2347@eggly.anvilsSigned-off-by:
Hugh Dickins <hughd@google.com> Signed-off-by:
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Roman Gushchin authored
This commit implements SLUB version of the obj_to_index() function, which will be required to calculate the offset of obj_cgroup in the obj_cgroups vector to store/obtain the objcg ownership data. To make it faster, let's repeat the SLAB's trick introduced by commit 6a2d7a95 ("SLAB: use a multiply instead of a divide in obj_to_index()") and avoid an expensive division. Vlastimil Babka noticed, that SLUB does have already a similar function called slab_index(), which is defined only if SLUB_DEBUG is enabled. The function does a similar math, but with a division, and it also takes a page address instead of a page pointer. Let's remove slab_index() and replace it with the new helper __obj_to_index(), which takes a page address. obj_to_index() will be a simple wrapper taking a page pointer and passing page_address(page) into __obj_to_index(). Signed-off-by:
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Roman Gushchin authored
In order to prepare for per-object slab memory accounting, convert NR_SLAB_RECLAIMABLE and NR_SLAB_UNRECLAIMABLE vmstat items to bytes. To make it obvious, rename them to NR_SLAB_RECLAIMABLE_B and NR_SLAB_UNRECLAIMABLE_B (similar to NR_KERNEL_STACK_KB). Internally global and per-node counters are stored in pages, however memcg and lruvec counters are stored in bytes. This scheme may look weird, but only for now. As soon as slab pages will be shared between multiple cgroups, global and node counters will reflect the total number of slab pages. However memcg and lruvec counters will be used for per-memcg slab memory tracking, which will take separate kernel objects in the account. Keeping global and node counters in pages helps to avoid additional overhead. The size of slab memory shouldn't exceed 4Gb on 32-bit machines, so it will fit into atomic_long_t we use for vmstats. Signed-off-by:
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Roman Gushchin authored
To implement per-object slab memory accounting, we need to convert slab vmstat counters to bytes. Actually, out of 4 levels of counters: global, per-node, per-memcg and per-lruvec only two last levels will require byte-sized counters. It's because global and per-node counters will be counting the number of slab pages, and per-memcg and per-lruvec will be counting the amount of memory taken by charged slab objects. Converting all vmstat counters to bytes or even all slab counters to bytes would introduce an additional overhead. So instead let's store global and per-node counters in pages, and memcg and lruvec counters in bytes. To make the API clean all access helpers (both on the read and write sides) are dealing with bytes. To avoid back-and-forth conversions a new flavor of read-side helpers is introduced, which always returns values in pages: node_page_state_pages() and global_node_page_state_pages(). Actually new helpers are just reading raw values. Old helpers are simple wrappers, which will complain on an attempt to read byte value, because at the moment no one actually needs bytes. Thanks to Johannes Weiner for the idea of having the byte-sized API on top of the page-sized internal storage. Signed-off-by:
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Roman Gushchin authored
Patch series "The new cgroup slab memory controller", v7. The patchset moves the accounting from the page level to the object level. It allows to share slab pages between memory cgroups. This leads to a significant win in the slab utilization (up to 45%) and the corresponding drop in the total kernel memory footprint. The reduced number of unmovable slab pages should also have a positive effect on the memory fragmentation. The patchset makes the slab accounting code simpler: there is no more need in the complicated dynamic creation and destruction of per-cgroup slab caches, all memory cgroups use a global set of shared slab caches. The lifetime of slab caches is not more connected to the lifetime of memory cgroups. The more precise accounting does require more CPU, however in practice the difference seems to be negligible. We've been using the new slab controller in Facebook production for several months with different workloads and haven't seen any noticeable regressions. What we've seen were memory savings in order of 1 GB per host (it varied heavily depending on the actual workload, size of RAM, number of CPUs, memory pressure, etc). The third version of the patchset added yet another step towards the simplification of the code: sharing of slab caches between accounted and non-accounted allocations. It comes with significant upsides (most noticeable, a complete elimination of dynamic slab caches creation) but not without some regression risks, so this change sits on top of the patchset and is not completely merged in. So in the unlikely event of a noticeable performance regression it can be reverted separately. The slab memory accounting works in exactly the same way for SLAB and SLUB. With both allocators the new controller shows significant memory savings, with SLUB the difference is bigger. On my 16-core desktop machine running Fedora 32 the size of the slab memory measured after the start of the system was lower by 58% and 38% with SLUB and SLAB correspondingly. As an estimation of a potential CPU overhead, below are results of slab_bulk_test01 test, kindly provided by Jesper D. Brouer. He also helped with the evaluation of results. The test can be found here: https://github.com/netoptimizer/prototype-kernel/ The smallest number in each row should be picked for a comparison. SLUB-patched - bulk-API - SLUB-patched : bulk_quick_reuse objects=1 : 187 - 90 - 224 cycles(tsc) - SLUB-patched : bulk_quick_reuse objects=2 : 110 - 53 - 133 cycles(tsc) - SLUB-patched : bulk_quick_reuse objects=3 : 88 - 95 - 42 cycles(tsc) - SLUB-patched : bulk_quick_reuse objects=4 : 91 - 85 - 36 cycles(tsc) - SLUB-patched : bulk_quick_reuse objects=8 : 32 - 66 - 32 cycles(tsc) SLUB-original - bulk-API - SLUB-original: bulk_quick_reuse objects=1 : 87 - 87 - 142 cycles(tsc) - SLUB-original: bulk_quick_reuse objects=2 : 52 - 53 - 53 cycles(tsc) - SLUB-original: bulk_quick_reuse objects=3 : 42 - 42 - 91 cycles(tsc) - SLUB-original: bulk_quick_reuse objects=4 : 91 - 37 - 37 cycles(tsc) - SLUB-original: bulk_quick_reuse objects=8 : 31 - 79 - 76 cycles(tsc) SLAB-patched - bulk-API - SLAB-patched : bulk_quick_reuse objects=1 : 67 - 67 - 140 cycles(tsc) - SLAB-patched : bulk_quick_reuse objects=2 : 55 - 46 - 46 cycles(tsc) - SLAB-patched : bulk_quick_reuse objects=3 : 93 - 94 - 39 cycles(tsc) - SLAB-patched : bulk_quick_reuse objects=4 : 35 - 88 - 85 cycles(tsc) - SLAB-patched : bulk_quick_reuse objects=8 : 30 - 30 - 30 cycles(tsc) SLAB-original- bulk-API - SLAB-original: bulk_quick_reuse objects=1 : 143 - 136 - 67 cycles(tsc) - SLAB-original: bulk_quick_reuse objects=2 : 45 - 46 - 46 cycles(tsc) - SLAB-original: bulk_quick_reuse objects=3 : 38 - 39 - 39 cycles(tsc) - SLAB-original: bulk_quick_reuse objects=4 : 35 - 87 - 87 cycles(tsc) - SLAB-original: bulk_quick_reuse objects=8 : 29 - 66 - 30 cycles(tsc) This patch (of 19): To convert memcg and lruvec slab counters to bytes there must be a way to change these counters without touching node counters. Factor out __mod_memcg_lruvec_state() out of __mod_lruvec_state(). Signed-off-by:
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Roman Gushchin authored
Historically the kernel memory accounting was an opt-in feature, which could be enabled for individual cgroups. But now it's not true, and it's on by default both on cgroup v1 and cgroup v2. And as long as a user has at least one non-root memory cgroup, the kernel memory accounting is on. So in most setups it's either always on (if memory cgroups are in use and kmem accounting is not disabled), either always off (otherwise). memcg_kmem_enabled() is used in many places to guard the kernel memory accounting code. If memcg_kmem_enabled() can reverse from returning true to returning false (as now), we can't rely on it on release paths and have to check if it was on before. If we'll make memcg_kmem_enabled() irreversible (always returning true after returning it for the first time), it'll make the general logic more simple and robust. It also will allow to guard some checks which otherwise would stay unguarded. Reported-by:
Naresh Kamboju <naresh.kamboju@linaro.org> Signed-off-by:
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Chris Down authored
The default is still set to inode32 for backwards compatibility, but system administrators can opt in to the new 64-bit inode numbers by either: 1. Passing inode64 on the command line when mounting, or 2. Configuring the kernel with CONFIG_TMPFS_INODE64=y The inode64 and inode32 names are used based on existing precedent from XFS. [hughd@google.com: Kconfig fixes] Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2008011928010.13320@eggly.anvilsSigned-off-by:
Amir Goldstein <amir73il@gmail.com> Acked-by:
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Chris Down authored
Patch series "tmpfs: inode: Reduce risk of inum overflow", v7. In Facebook production we are seeing heavy i_ino wraparounds on tmpfs. On affected tiers, in excess of 10% of hosts show multiple files with different content and the same inode number, with some servers even having as many as 150 duplicated inode numbers with differing file content. This causes actual, tangible problems in production. For example, we have complaints from those working on remote caches that their application is reporting cache corruptions because it uses (device, inodenum) to establish the identity of a particular cache object, but because it's not unique any more, the application refuses to continue and reports cache corruption. Even worse, sometimes applications may not even detect the corruption but may continue anyway, causing phantom and hard to debug behaviour. In general, userspace applications expect that (device, inodenum) should be enough to be uniquely point to one inode, which seems fair enough. One might also need to check the generation, but in this case: 1. That's not currently exposed to userspace (ioctl(...FS_IOC_GETVERSION...) returns ENOTTY on tmpfs); 2. Even with generation, there shouldn't be two live inodes with the same inode number on one device. In order to mitigate this, we take a two-pronged approach: 1. Moving inum generation from being global to per-sb for tmpfs. This itself allows some reduction in i_ino churn. This works on both 64- and 32- bit machines. 2. Adding inode{64,32} for tmpfs. This fix is supported on machines with 64-bit ino_t only: we allow users to mount tmpfs with a new inode64 option that uses the full width of ino_t, or CONFIG_TMPFS_INODE64. You can see how this compares to previous related patches which didn't implement this per-superblock: - https://patchwork.kernel.org/patch/11254001/ - https://patchwork.kernel.org/patch/11023915/ This patch (of 2): get_next_ino has a number of problems: - It uses and returns a uint, which is susceptible to become overflowed if a lot of volatile inodes that use get_next_ino are created. - It's global, with no specificity per-sb or even per-filesystem. This means it's not that difficult to cause inode number wraparounds on a single device, which can result in having multiple distinct inodes with the same inode number. This patch adds a per-superblock counter that mitigates the second case. This design also allows us to later have a specific i_ino size per-device, for example, allowing users to choose whether to use 32- or 64-bit inodes for each tmpfs mount. This is implemented in the next commit. For internal shmem mounts which may be less tolerant to spinlock delays, we implement a percpu batching scheme which only takes the stat_lock at each batch boundary. Signed-off-by: -
Xianting Tian authored
swap_readpage() does the sync io for one page, the io is not big, normally, the io can be finished quickly, but it may take long time or wait forever in case of io failure or discard. This patch uses blk_io_schedule() instead of io_schedule() to avoid task hung and crash (when set /proc/sys/kernel/hung_task_panic) when the above exception occurs. This is similar to the hung task avoidance in submit_bio_wait(), blk_execute_rq() and __blkdev_direct_IO(). Signed-off-by:
Xianting Tian <xianting_tian@126.com> Signed-off-by:
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Krzysztof Kozlowski authored
Fix W=1 compile warnings (invalid kerneldoc): mm/swap_state.c:742: warning: Function parameter or member 'fentry' not described in 'swap_vma_readahead' mm/swap_state.c:742: warning: Excess function parameter 'entry' description in 'swap_vma_readahead' Signed-off-by:Krzysztof Kozlowski <krzk@kernel.org> Signed-off-by:
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Zhen Lei authored
Because enable_swap_slots_cache can only become true in enable_swap_slots_cache(), and depends on swap_slot_cache_initialized is true before. That means, when enable_swap_slots_cache is true, swap_slot_cache_initialized is true also. So the condition: "swap_slot_cache_enabled && swap_slot_cache_initialized" can be reduced to "swap_slot_cache_enabled" And in mathematics: "!swap_slot_cache_enabled || !swap_slot_cache_initialized" is equal to "!(swap_slot_cache_enabled && swap_slot_cache_initialized)" So no functional change. Signed-off-by:
Zhen Lei <thunder.leizhen@huawei.com> Signed-off-by:
Tim Chen <tim.c.chen@linux.intel.com> Link: http://lkml.kernel.org/r/20200430061143.450-4-thunder.leizhen@huawei.comSigned-off-by:
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