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authorNhat Pham <nphamcs@gmail.com>2023-10-06 21:46:28 +0300
committerAndrew Morton <akpm@linux-foundation.org>2023-10-19 00:34:17 +0300
commit8cba9576df601c384abd334a503c3f6e1e29eefb (patch)
tree06fb669c3aa1d6ff6ef51c7dd6d954892b8dea79 /mm/migrate.c
parent85ce2c517ade0d51b7ad95f2e88be9bbe294379a (diff)
downloadlinux-8cba9576df601c384abd334a503c3f6e1e29eefb.tar.xz
hugetlb: memcg: account hugetlb-backed memory in memory controller
Currently, hugetlb memory usage is not acounted for in the memory controller, which could lead to memory overprotection for cgroups with hugetlb-backed memory. This has been observed in our production system. For instance, here is one of our usecases: suppose there are two 32G containers. The machine is booted with hugetlb_cma=6G, and each container may or may not use up to 3 gigantic page, depending on the workload within it. The rest is anon, cache, slab, etc. We can set the hugetlb cgroup limit of each cgroup to 3G to enforce hugetlb fairness. But it is very difficult to configure memory.max to keep overall consumption, including anon, cache, slab etc. fair. What we have had to resort to is to constantly poll hugetlb usage and readjust memory.max. Similar procedure is done to other memory limits (memory.low for e.g). However, this is rather cumbersome and buggy. Furthermore, when there is a delay in memory limits correction, (for e.g when hugetlb usage changes within consecutive runs of the userspace agent), the system could be in an over/underprotected state. This patch rectifies this issue by charging the memcg when the hugetlb folio is utilized, and uncharging when the folio is freed (analogous to the hugetlb controller). Note that we do not charge when the folio is allocated to the hugetlb pool, because at this point it is not owned by any memcg. Some caveats to consider: * This feature is only available on cgroup v2. * There is no hugetlb pool management involved in the memory controller. As stated above, hugetlb folios are only charged towards the memory controller when it is used. Host overcommit management has to consider it when configuring hard limits. * Failure to charge towards the memcg results in SIGBUS. This could happen even if the hugetlb pool still has pages (but the cgroup limit is hit and reclaim attempt fails). * When this feature is enabled, hugetlb pages contribute to memory reclaim protection. low, min limits tuning must take into account hugetlb memory. * Hugetlb pages utilized while this option is not selected will not be tracked by the memory controller (even if cgroup v2 is remounted later on). Link: https://lkml.kernel.org/r/20231006184629.155543-4-nphamcs@gmail.com Signed-off-by: Nhat Pham <nphamcs@gmail.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Frank van der Linden <fvdl@google.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Muchun Song <muchun.song@linux.dev> Cc: Rik van Riel <riel@surriel.com> Cc: Roman Gushchin <roman.gushchin@linux.dev> Cc: Shakeel Butt <shakeelb@google.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Tejun heo <tj@kernel.org> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Zefan Li <lizefan.x@bytedance.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/migrate.c')
-rw-r--r--mm/migrate.c3
1 files changed, 1 insertions, 2 deletions
diff --git a/mm/migrate.c b/mm/migrate.c
index 9d9eee5322d1..c602bf6dec97 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -633,8 +633,7 @@ void folio_migrate_flags(struct folio *newfolio, struct folio *folio)
folio_copy_owner(newfolio, folio);
- if (!folio_test_hugetlb(folio))
- mem_cgroup_migrate(folio, newfolio);
+ mem_cgroup_migrate(folio, newfolio);
}
EXPORT_SYMBOL(folio_migrate_flags);