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* mm: page_counter: remove unneeded atomic ops for low/minShakeel Butt2022-09-111-7/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Patch series "memcg: optimize charge codepath", v2. Recently Linux networking stack has moved from a very old per socket pre-charge caching to per-cpu caching to avoid pre-charge fragmentation and unwarranted OOMs. One impact of this change is that for network traffic workloads, memcg charging codepath can become a bottleneck. The kernel test robot has also reported this regression[1]. This patch series tries to improve the memcg charging for such workloads. This patch series implement three optimizations: (A) Reduce atomic ops in page counter update path. (B) Change layout of struct page_counter to eliminate false sharing between usage and high. (C) Increase the memcg charge batch to 64. To evaluate the impact of these optimizations, on a 72 CPUs machine, we ran the following workload in root memcg and then compared with scenario where the workload is run in a three level of cgroup hierarchy with top level having min and low setup appropriately. $ netserver -6 # 36 instances of netperf with following params $ netperf -6 -H ::1 -l 60 -t TCP_SENDFILE -- -m 10K Results (average throughput of netperf): 1. root memcg 21694.8 Mbps 2. 6.0-rc1 10482.7 Mbps (-51.6%) 3. 6.0-rc1 + (A) 14542.5 Mbps (-32.9%) 4. 6.0-rc1 + (B) 12413.7 Mbps (-42.7%) 5. 6.0-rc1 + (C) 17063.7 Mbps (-21.3%) 6. 6.0-rc1 + (A+B+C) 20120.3 Mbps (-7.2%) With all three optimizations, the memcg overhead of this workload has been reduced from 51.6% to just 7.2%. [1] https://lore.kernel.org/linux-mm/20220619150456.GB34471@xsang-OptiPlex-9020/ This patch (of 3): For cgroups using low or min protections, the function propagate_protected_usage() was doing an atomic xchg() operation irrespectively. We can optimize out this atomic operation for one specific scenario where the workload is using the protection (i.e. min > 0) and the usage is above the protection (i.e. usage > min). This scenario is actually very common where the users want a part of their workload to be protected against the external reclaim. Though this optimization does introduce a race when the usage is around the protection and concurrent charges and uncharged trip it over or under the protection. In such cases, we might see lower effective protection but the subsequent charge/uncharge will correct it. To evaluate the impact of this optimization, on a 72 CPUs machine, we ran the following workload in a three level of cgroup hierarchy with top level having min and low setup appropriately to see if this optimization is effective for the mentioned case. $ netserver -6 # 36 instances of netperf with following params $ netperf -6 -H ::1 -l 60 -t TCP_SENDFILE -- -m 10K Results (average throughput of netperf): Without (6.0-rc1) 10482.7 Mbps With patch 14542.5 Mbps (38.7% improvement) With the patch, the throughput improved by 38.7% Link: https://lkml.kernel.org/r/20220825000506.239406-1-shakeelb@google.com Link: https://lkml.kernel.org/r/20220825000506.239406-2-shakeelb@google.com Signed-off-by: Shakeel Butt <shakeelb@google.com> Reported-by: kernel test robot <oliver.sang@intel.com> Acked-by: Soheil Hassas Yeganeh <soheil@google.com> Reviewed-by: Feng Tang <feng.tang@intel.com> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Eric Dumazet <edumazet@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: "Michal Koutný" <mkoutny@suse.com> Cc: Muchun Song <songmuchun@bytedance.com> Cc: Oliver Sang <oliver.sang@intel.com> Cc: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* mm: skip retry when new limit is not below old one in page_counter_set_maxBui Quang Minh2022-09-111-1/+1
| | | | | | | | | | | | | | | | In page_counter_set_max, we want to make sure the new limit is not below the concurrently-changing counter value. We read the counter and check that the limit is not below the counter before the swap. After the swap, we read the counter again and retry in case the counter is incremented as this may violate the requirement. Even though the page_counter_try_charge can see the old limit, it is guaranteed that the counter is not above the old limit after the increment. So in case the new limit is not below the old limit, the counter is guaranteed to be not above the new limit too. We can skip the retry in this case to optimize a little bit. Link: https://lkml.kernel.org/r/20220821154055.109635-1-minhquangbui99@gmail.com Signed-off-by: Bui Quang Minh <minhquangbui99@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* mm/page_counter: remove an incorrect call to propagate_protected_usage()Donghai Qiao2022-01-151-1/+0
| | | | | | | | | | | | | | | propagate_protected_usage() is called to propagate the usage change in the page_counter structure. But there is a call to this function from page_counter_try_charge() when there is actually no usage change. Hence this call should be removed. Link: https://lkml.kernel.org/r/20211118181125.3918222-1-dqiao@redhat.com Signed-off-by: Donghai Qiao <dqiao@redhat.com> Reviewed-by: Roman Gushchin <guro@fb.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* mm: page_counter: mitigate consequences of a page_counter underflowJohannes Weiner2021-04-301-2/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | When the unsigned page_counter underflows, even just by a few pages, a cgroup will not be able to run anything afterwards and trigger the OOM killer in a loop. Underflows shouldn't happen, but when they do in practice, we may just be off by a small amount that doesn't interfere with the normal operation - consequences don't need to be that dire. Reset the page_counter to 0 upon underflow. We'll issue a warning that the accounting will be off and then try to keep limping along. [ We used to do this with the original res_counter, where it was a more straight-forward correction inside the spinlock section. I didn't carry it forward into the lockless page counters for simplicity, but it turns out this is quite useful in practice. ] Link: https://lkml.kernel.org/r/20210408143155.2679744-1-hannes@cmpxchg.org Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Chris Down <chris@chrisdown.name> Reviewed-by: Shakeel Butt <shakeelb@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Roman Gushchin <guro@fb.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* mm/page_counter: use page_counter_read in page_counter_set_maxHui Su2020-12-151-2/+2
| | | | | | | | | | Use page_counter_read() in page_counter_set_max(). Link: https://lkml.kernel.org/r/20201113141048.GA178922@rlk Signed-off-by: Hui Su <sh_def@163.com> Reviewed-by: Pankaj Gupta <pankaj.gupta@cloud.ionos.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* mm/page_counter: correct the obsolete func name in the comment of ↵Miaohe Lin2020-10-131-1/+1
| | | | | | | | | | | | | | | page_counter_try_charge() Since commit bbec2e15170a ("mm: rename page_counter's count/limit into usage/max"), page_counter_limit() is renamed to page_counter_set_max(). So replace page_counter_limit with page_counter_set_max in comment. Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Roman Gushchin <guro@fb.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Link: https://lkml.kernel.org/r/20200917113629.14382-1-linmiaohe@huawei.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* mm/page_counter: fix various data races at memswQian Cai2020-08-141-6/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit 3e32cb2e0a12 ("mm: memcontrol: lockless page counters") could had memcg->memsw->watermark and memcg->memsw->failcnt been accessed concurrently as reported by KCSAN, BUG: KCSAN: data-race in page_counter_try_charge / page_counter_try_charge read to 0xffff8fb18c4cd190 of 8 bytes by task 1081 on cpu 59: page_counter_try_charge+0x4d/0x150 mm/page_counter.c:138 try_charge+0x131/0xd50 mm/memcontrol.c:2405 __memcg_kmem_charge_memcg+0x58/0x140 __memcg_kmem_charge+0xcc/0x280 __alloc_pages_nodemask+0x1e1/0x450 alloc_pages_current+0xa6/0x120 pte_alloc_one+0x17/0xd0 __pte_alloc+0x3a/0x1f0 copy_p4d_range+0xc36/0x1990 copy_page_range+0x21d/0x360 dup_mmap+0x5f5/0x7a0 dup_mm+0xa2/0x240 copy_process+0x1b3f/0x3460 _do_fork+0xaa/0xa20 __x64_sys_clone+0x13b/0x170 do_syscall_64+0x91/0xb47 entry_SYSCALL_64_after_hwframe+0x49/0xbe write to 0xffff8fb18c4cd190 of 8 bytes by task 1153 on cpu 120: page_counter_try_charge+0x5b/0x150 mm/page_counter.c:139 try_charge+0x131/0xd50 mm/memcontrol.c:2405 mem_cgroup_try_charge+0x159/0x460 mem_cgroup_try_charge_delay+0x3d/0xa0 wp_page_copy+0x14d/0x930 do_wp_page+0x107/0x7b0 __handle_mm_fault+0xce6/0xd40 handle_mm_fault+0xfc/0x2f0 do_page_fault+0x263/0x6f9 page_fault+0x34/0x40 BUG: KCSAN: data-race in page_counter_try_charge / page_counter_try_charge write to 0xffff88809bbf2158 of 8 bytes by task 11782 on cpu 0: page_counter_try_charge+0x100/0x170 mm/page_counter.c:129 try_charge+0x185/0xbf0 mm/memcontrol.c:2405 __memcg_kmem_charge_memcg+0x4a/0xe0 mm/memcontrol.c:2837 __memcg_kmem_charge+0xcf/0x1b0 mm/memcontrol.c:2877 __alloc_pages_nodemask+0x26c/0x310 mm/page_alloc.c:4780 read to 0xffff88809bbf2158 of 8 bytes by task 11814 on cpu 1: page_counter_try_charge+0xef/0x170 mm/page_counter.c:129 try_charge+0x185/0xbf0 mm/memcontrol.c:2405 __memcg_kmem_charge_memcg+0x4a/0xe0 mm/memcontrol.c:2837 __memcg_kmem_charge+0xcf/0x1b0 mm/memcontrol.c:2877 __alloc_pages_nodemask+0x26c/0x310 mm/page_alloc.c:4780 Since watermark could be compared or set to garbage due to a data race which would change the code logic, fix it by adding a pair of READ_ONCE() and WRITE_ONCE() in those places. The "failcnt" counter is tolerant of some degree of inaccuracy and is only used to report stats, a data race will not be harmful, thus mark it as an intentional data race using the data_race() macro. Fixes: 3e32cb2e0a12 ("mm: memcontrol: lockless page counters") Reported-by: syzbot+f36cfe60b1006a94f9dc@syzkaller.appspotmail.com Signed-off-by: Qian Cai <cai@lca.pw> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Michal Hocko <mhocko@suse.com> Cc: David Hildenbrand <david@redhat.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Marco Elver <elver@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Link: http://lkml.kernel.org/r/1581519682-23594-1-git-send-email-cai@lca.pw Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* mm/page_counter.c: fix protection usage propagationMichal Koutný2020-08-071-3/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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: 230671533d64 ("mm: memory.low hierarchical behavior") Signed-off-by: Michal Koutný <mkoutny@suse.com> Signed-off-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Michal Hocko <mhocko@suse.com> Acked-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.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* mm, memcg: prevent memory.min load/store tearingChris Down2020-04-021-4/+5
| | | | | | | | | | | | | | This can be set concurrently with reads, which may cause the wrong value to be propagated. Signed-off-by: Chris Down <chris@chrisdown.name> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Roman Gushchin <guro@fb.com> Cc: Tejun Heo <tj@kernel.org> Link: http://lkml.kernel.org/r/e809b4e6b0c1626dac6945970de06409a180ee65.1584034301.git.chris@chrisdown.name Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* mm, memcg: prevent memory.low load/store tearingChris Down2020-04-021-3/+5
| | | | | | | | | | | | | | This can be set concurrently with reads, which may cause the wrong value to be propagated. Signed-off-by: Chris Down <chris@chrisdown.name> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Roman Gushchin <guro@fb.com> Cc: Tejun Heo <tj@kernel.org> Link: http://lkml.kernel.org/r/448206f44b0fa7be9dad2ca2601d2bcb2c0b7844.1584034301.git.chris@chrisdown.name Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* mm: memcontrol: fix memory.low proportional distributionJohannes Weiner2020-04-021-10/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Patch series "mm: memcontrol: recursive memory.low protection", v3. The current memory.low (and memory.min) semantics require protection to be assigned to a cgroup in an untinterrupted chain from the top-level cgroup all the way to the leaf. In practice, we want to protect entire cgroup subtrees from each other (system management software vs. workload), but we would like the VM to balance memory optimally *within* each subtree, without having to make explicit weight allocations among individual components. The current semantics make that impossible. They also introduce unmanageable complexity into more advanced resource trees. For example: host root `- system.slice `- rpm upgrades `- logging `- workload.slice `- a container `- system.slice `- workload.slice `- job A `- component 1 `- component 2 `- job B At a host-level perspective, we would like to protect the outer workload.slice subtree as a whole from rpm upgrades, logging etc. But for that to be effective, right now we'd have to propagate it down through the container, the inner workload.slice, into the job cgroup and ultimately the component cgroups where memory is actually, physically allocated. This may cross several tree delegation points and namespace boundaries, which make such a setup near impossible. CPU and IO on the other hand are already distributed recursively. The user would simply configure allowances at the host level, and they would apply to the entire subtree without any downward propagation. To enable the above-mentioned usecases and bring memory in line with other resource controllers, this patch series extends memory.low/min such that settings apply recursively to the entire subtree. Users can still assign explicit shares in subgroups, but if they don't, any ancestral protection will be distributed such that children compete freely amongst each other - as if no memory control were enabled inside the subtree - but enjoy protection from neighboring trees. In the above example, the user would then be able to configure shares of CPU, IO and memory at the host level to comprehensively protect and isolate the workload.slice as a whole from system.slice activity. Patch #1 fixes an existing bug that can give a cgroup tree more protection than it should receive as per ancestor configuration. Patch #2 simplifies and documents the existing code to make it easier to reason about the changes in the next patch. Patch #3 finally implements recursive memory protection semantics. Because of a risk of regressing legacy setups, the new semantics are hidden behind a cgroup2 mount option, 'memory_recursiveprot'. More details in patch #3. This patch (of 3): When memory.low is overcommitted - i.e. the children claim more protection than their shared ancestor grants them - the allowance is distributed in proportion to how much each sibling uses their own declared protection: low_usage = min(memory.low, memory.current) elow = parent_elow * (low_usage / siblings_low_usage) However, siblings_low_usage is not the sum of all low_usages. It sums up the usages of *only those cgroups that are within their memory.low* That means that low_usage can be *bigger* than siblings_low_usage, and consequently the total protection afforded to the children can be bigger than what the ancestor grants the subtree. Consider three groups where two are in excess of their protection: A/memory.low = 10G A/A1/memory.low = 10G, memory.current = 20G A/A2/memory.low = 10G, memory.current = 20G A/A3/memory.low = 10G, memory.current = 8G siblings_low_usage = 8G (only A3 contributes) A1/elow = parent_elow(10G) * low_usage(10G) / siblings_low_usage(8G) = 12.5G -> 10G A2/elow = parent_elow(10G) * low_usage(10G) / siblings_low_usage(8G) = 12.5G -> 10G A3/elow = parent_elow(10G) * low_usage(8G) / siblings_low_usage(8G) = 10.0G (the 12.5G are capped to the explicit memory.low setting of 10G) With that, the sum of all awarded protection below A is 30G, when A only grants 10G for the entire subtree. What does this mean in practice? A1 and A2 would still be in excess of their 10G allowance and would be reclaimed, whereas A3 would not. As they eventually drop below their protection setting, they would be counted in siblings_low_usage again and the error would right itself. When reclaim was applied in a binary fashion (cgroup is reclaimed when it's above its protection, otherwise it's skipped) this would actually work out just fine. However, since 1bc63fb1272b ("mm, memcg: make scan aggression always exclude protection"), reclaim pressure is scaled to how much a cgroup is above its protection. As a result this calculation error unduly skews pressure away from A1 and A2 toward the rest of the system. But why did we do it like this in the first place? The reasoning behind exempting groups in excess from siblings_low_usage was to go after them first during reclaim in an overcommitted subtree: A/memory.low = 2G, memory.current = 4G A/A1/memory.low = 3G, memory.current = 2G A/A2/memory.low = 1G, memory.current = 2G siblings_low_usage = 2G (only A1 contributes) A1/elow = parent_elow(2G) * low_usage(2G) / siblings_low_usage(2G) = 2G A2/elow = parent_elow(2G) * low_usage(1G) / siblings_low_usage(2G) = 1G While the children combined are overcomitting A and are technically both at fault, A2 is actively declaring unprotected memory and we would like to reclaim that first. However, while this sounds like a noble goal on the face of it, it doesn't make much difference in actual memory distribution: Because A is overcommitted, reclaim will not stop once A2 gets pushed back to within its allowance; we'll have to reclaim A1 either way. The end result is still that protection is distributed proportionally, with A1 getting 3/4 (1.5G) and A2 getting 1/4 (0.5G) of A's allowance. [ If A weren't overcommitted, it wouldn't make a difference since each cgroup would just get the protection it declares: A/memory.low = 2G, memory.current = 3G A/A1/memory.low = 1G, memory.current = 1G A/A2/memory.low = 1G, memory.current = 2G With the current calculation: siblings_low_usage = 1G (only A1 contributes) A1/elow = parent_elow(2G) * low_usage(1G) / siblings_low_usage(1G) = 2G -> 1G A2/elow = parent_elow(2G) * low_usage(1G) / siblings_low_usage(1G) = 2G -> 1G Including excess groups in siblings_low_usage: siblings_low_usage = 2G A1/elow = parent_elow(2G) * low_usage(1G) / siblings_low_usage(2G) = 1G -> 1G A2/elow = parent_elow(2G) * low_usage(1G) / siblings_low_usage(2G) = 1G -> 1G ] Simplify the calculation and fix the proportional reclaim bug by including excess cgroups in siblings_low_usage. After this patch, the effective memory.low distribution from the example above would be as follows: A/memory.low = 10G A/A1/memory.low = 10G, memory.current = 20G A/A2/memory.low = 10G, memory.current = 20G A/A3/memory.low = 10G, memory.current = 8G siblings_low_usage = 28G A1/elow = parent_elow(10G) * low_usage(10G) / siblings_low_usage(28G) = 3.5G A2/elow = parent_elow(10G) * low_usage(10G) / siblings_low_usage(28G) = 3.5G A3/elow = parent_elow(10G) * low_usage(8G) / siblings_low_usage(28G) = 2.8G Fixes: 1bc63fb1272b ("mm, memcg: make scan aggression always exclude protection") Fixes: 230671533d64 ("mm: memory.low hierarchical behavior") Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Tejun Heo <tj@kernel.org> Acked-by: Roman Gushchin <guro@fb.com> Acked-by: Chris Down <chris@chrisdown.name> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Michal Koutný <mkoutny@suse.com> Link: http://lkml.kernel.org/r/20200227195606.46212-2-hannes@cmpxchg.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* memcg: introduce memory.minRoman Gushchin2018-06-071-17/+46
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Memory controller implements the memory.low best-effort memory protection mechanism, which works perfectly in many cases and allows protecting working sets of important workloads from sudden reclaim. But its semantics has a significant limitation: it works only as long as there is a supply of reclaimable memory. This makes it pretty useless against any sort of slow memory leaks or memory usage increases. This is especially true for swapless systems. If swap is enabled, memory soft protection effectively postpones problems, allowing a leaking application to fill all swap area, which makes no sense. The only effective way to guarantee the memory protection in this case is to invoke the OOM killer. It's possible to handle this case in userspace by reacting on MEMCG_LOW events; but there is still a place for a fail-safe in-kernel mechanism to provide stronger guarantees. This patch introduces the memory.min interface for cgroup v2 memory controller. It works very similarly to memory.low (sharing the same hierarchical behavior), except that it's not disabled if there is no more reclaimable memory in the system. If cgroup is not populated, its memory.min is ignored, because otherwise even the OOM killer wouldn't be able to reclaim the protected memory, and the system can stall. [guro@fb.com: s/low/min/ in docs] Link: http://lkml.kernel.org/r/20180510130758.GA9129@castle.DHCP.thefacebook.com Link: http://lkml.kernel.org/r/20180509180734.GA4856@castle.DHCP.thefacebook.com Signed-off-by: Roman Gushchin <guro@fb.com> Reviewed-by: Randy Dunlap <rdunlap@infradead.org> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* mm: memory.low hierarchical behaviorRoman Gushchin2018-06-071-0/+43
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch aims to address an issue in current memory.low semantics, which makes it hard to use it in a hierarchy, where some leaf memory cgroups are more valuable than others. For example, there are memcgs A, A/B, A/C, A/D and A/E: A A/memory.low = 2G, A/memory.current = 6G //\\ BC DE B/memory.low = 3G B/memory.current = 2G C/memory.low = 1G C/memory.current = 2G D/memory.low = 0 D/memory.current = 2G E/memory.low = 10G E/memory.current = 0 If we apply memory pressure, B, C and D are reclaimed at the same pace while A's usage exceeds 2G. This is obviously wrong, as B's usage is fully below B's memory.low, and C has 1G of protection as well. Also, A is pushed to the size, which is less than A's 2G memory.low, which is also wrong. A simple bash script (provided below) can be used to reproduce the problem. Current results are: A: 1430097920 A/B: 711929856 A/C: 717426688 A/D: 741376 A/E: 0 To address the issue a concept of effective memory.low is introduced. Effective memory.low is always equal or less than original memory.low. In a case, when there is no memory.low overcommittment (and also for top-level cgroups), these two values are equal. Otherwise it's a part of parent's effective memory.low, calculated as a cgroup's memory.low usage divided by sum of sibling's memory.low usages (under memory.low usage I mean the size of actually protected memory: memory.current if memory.current < memory.low, 0 otherwise). It's necessary to track the actual usage, because otherwise an empty cgroup with memory.low set (A/E in my example) will affect actual memory distribution, which makes no sense. To avoid traversing the cgroup tree twice, page_counters code is reused. Calculating effective memory.low can be done in the reclaim path, as we conveniently traversing the cgroup tree from top to bottom and check memory.low on each level. So, it's a perfect place to calculate effective memory low and save it to use it for children cgroups. This also eliminates a need to traverse the cgroup tree from bottom to top each time to check if parent's guarantee is not exceeded. Setting/resetting effective memory.low is intentionally racy, but it's fine and shouldn't lead to any significant differences in actual memory distribution. With this patch applied results are matching the expectations: A: 2147930112 A/B: 1428721664 A/C: 718393344 A/D: 815104 A/E: 0 Test script: #!/bin/bash CGPATH="/sys/fs/cgroup" truncate /file1 --size 2G truncate /file2 --size 2G truncate /file3 --size 2G truncate /file4 --size 50G mkdir "${CGPATH}/A" echo "+memory" > "${CGPATH}/A/cgroup.subtree_control" mkdir "${CGPATH}/A/B" "${CGPATH}/A/C" "${CGPATH}/A/D" "${CGPATH}/A/E" echo 2G > "${CGPATH}/A/memory.low" echo 3G > "${CGPATH}/A/B/memory.low" echo 1G > "${CGPATH}/A/C/memory.low" echo 0 > "${CGPATH}/A/D/memory.low" echo 10G > "${CGPATH}/A/E/memory.low" echo $$ > "${CGPATH}/A/B/cgroup.procs" && vmtouch -qt /file1 echo $$ > "${CGPATH}/A/C/cgroup.procs" && vmtouch -qt /file2 echo $$ > "${CGPATH}/A/D/cgroup.procs" && vmtouch -qt /file3 echo $$ > "${CGPATH}/cgroup.procs" && vmtouch -qt /file4 echo "A: " `cat "${CGPATH}/A/memory.current"` echo "A/B: " `cat "${CGPATH}/A/B/memory.current"` echo "A/C: " `cat "${CGPATH}/A/C/memory.current"` echo "A/D: " `cat "${CGPATH}/A/D/memory.current"` echo "A/E: " `cat "${CGPATH}/A/E/memory.current"` rmdir "${CGPATH}/A/B" "${CGPATH}/A/C" "${CGPATH}/A/D" "${CGPATH}/A/E" rmdir "${CGPATH}/A" rm /file1 /file2 /file3 /file4 Link: http://lkml.kernel.org/r/20180405185921.4942-2-guro@fb.com Signed-off-by: Roman Gushchin <guro@fb.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* mm: rename page_counter's count/limit into usage/maxRoman Gushchin2018-06-071-14/+14
| | | | | | | | | | | | | | | | | | | | | | | | | | | This patch renames struct page_counter fields: count -> usage limit -> max and the corresponding functions: page_counter_limit() -> page_counter_set_max() mem_cgroup_get_limit() -> mem_cgroup_get_max() mem_cgroup_resize_limit() -> mem_cgroup_resize_max() memcg_update_kmem_limit() -> memcg_update_kmem_max() memcg_update_tcp_limit() -> memcg_update_tcp_max() The idea behind this renaming is to have the direct matching between memory cgroup knobs (low, high, max) and page_counters API. This is pure renaming, this patch doesn't bring any functional change. Link: http://lkml.kernel.org/r/20180405185921.4942-1-guro@fb.com Signed-off-by: Roman Gushchin <guro@fb.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* License cleanup: add SPDX GPL-2.0 license identifier to files with no licenseGreg Kroah-Hartman2017-11-021-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* mm: page_counter: let page_counter_try_charge() return boolJohannes Weiner2015-11-051-7/+7
| | | | | | | | | | | | | | page_counter_try_charge() currently returns 0 on success and -ENOMEM on failure, which is surprising behavior given the function name. Make it follow the expected pattern of try_stuff() functions that return a boolean true to indicate success, or false for failure. Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Vladimir Davydov <vdavydov@virtuozzo.com Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* mm: page_counter: pull "-1" handling out of page_counter_memparse()Johannes Weiner2015-02-111-3/+4
| | | | | | | | | | | | | The unified hierarchy interface for memory cgroups will no longer use "-1" to mean maximum possible resource value. In preparation for this, make the string an argument and let the caller supply it. Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@suse.cz> Cc: Vladimir Davydov <vdavydov@parallels.com> Cc: Greg Thelen <gthelen@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* mm: memcontrol: remove obsolete kmemcg pinning tricksJohannes Weiner2014-12-101-19/+4
| | | | | | | | | | | | | | | | | As charges now pin the css explicitely, there is no more need for kmemcg to acquire a proxy reference for outstanding pages during offlining, or maintain state to identify such "dead" groups. This was the last user of the uncharge functions' return values, so remove them as well. Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Vladimir Davydov <vdavydov@parallels.com> Acked-by: Michal Hocko <mhocko@suse.cz> Cc: David Rientjes <rientjes@google.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* mm: memcontrol: lockless page countersJohannes Weiner2014-12-101-0/+207
Memory is internally accounted in bytes, using spinlock-protected 64-bit counters, even though the smallest accounting delta is a page. The counter interface is also convoluted and does too many things. Introduce a new lockless word-sized page counter API, then change all memory accounting over to it. The translation from and to bytes then only happens when interfacing with userspace. The removed locking overhead is noticable when scaling beyond the per-cpu charge caches - on a 4-socket machine with 144-threads, the following test shows the performance differences of 288 memcgs concurrently running a page fault benchmark: vanilla: 18631648.500498 task-clock (msec) # 140.643 CPUs utilized ( +- 0.33% ) 1,380,638 context-switches # 0.074 K/sec ( +- 0.75% ) 24,390 cpu-migrations # 0.001 K/sec ( +- 8.44% ) 1,843,305,768 page-faults # 0.099 M/sec ( +- 0.00% ) 50,134,994,088,218 cycles # 2.691 GHz ( +- 0.33% ) <not supported> stalled-cycles-frontend <not supported> stalled-cycles-backend 8,049,712,224,651 instructions # 0.16 insns per cycle ( +- 0.04% ) 1,586,970,584,979 branches # 85.176 M/sec ( +- 0.05% ) 1,724,989,949 branch-misses # 0.11% of all branches ( +- 0.48% ) 132.474343877 seconds time elapsed ( +- 0.21% ) lockless: 12195979.037525 task-clock (msec) # 133.480 CPUs utilized ( +- 0.18% ) 832,850 context-switches # 0.068 K/sec ( +- 0.54% ) 15,624 cpu-migrations # 0.001 K/sec ( +- 10.17% ) 1,843,304,774 page-faults # 0.151 M/sec ( +- 0.00% ) 32,811,216,801,141 cycles # 2.690 GHz ( +- 0.18% ) <not supported> stalled-cycles-frontend <not supported> stalled-cycles-backend 9,999,265,091,727 instructions # 0.30 insns per cycle ( +- 0.10% ) 2,076,759,325,203 branches # 170.282 M/sec ( +- 0.12% ) 1,656,917,214 branch-misses # 0.08% of all branches ( +- 0.55% ) 91.369330729 seconds time elapsed ( +- 0.45% ) On top of improved scalability, this also gets rid of the icky long long types in the very heart of memcg, which is great for 32 bit and also makes the code a lot more readable. Notable differences between the old and new API: - res_counter_charge() and res_counter_charge_nofail() become page_counter_try_charge() and page_counter_charge() resp. to match the more common kernel naming scheme of try_do()/do() - res_counter_uncharge_until() is only ever used to cancel a local counter and never to uncharge bigger segments of a hierarchy, so it's replaced by the simpler page_counter_cancel() - res_counter_set_limit() is replaced by page_counter_limit(), which expects its callers to serialize against themselves - res_counter_memparse_write_strategy() is replaced by page_counter_limit(), which rounds down to the nearest page size - rather than up. This is more reasonable for explicitely requested hard upper limits. - to keep charging light-weight, page_counter_try_charge() charges speculatively, only to roll back if the result exceeds the limit. Because of this, a failing bigger charge can temporarily lock out smaller charges that would otherwise succeed. The error is bounded to the difference between the smallest and the biggest possible charge size, so for memcg, this means that a failing THP charge can send base page charges into reclaim upto 2MB (4MB) before the limit would have been reached. This should be acceptable. [akpm@linux-foundation.org: add includes for WARN_ON_ONCE and memparse] [akpm@linux-foundation.org: add includes for WARN_ON_ONCE, memparse, strncmp, and PAGE_SIZE] Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@suse.cz> Acked-by: Vladimir Davydov <vdavydov@parallels.com> Cc: Tejun Heo <tj@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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