The patch titled Subject: mm: memcontrol: do not acquire page_cgroup lock for kmem pages has been added to the -mm tree. Its filename is mm-memcontrol-do-not-acquire-page_cgroup-lock-for-kmem-pages.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mm-memcontrol-do-not-acquire-page_cgroup-lock-for-kmem-pages.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/mm-memcontrol-do-not-acquire-page_cgroup-lock-for-kmem-pages.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Johannes Weiner <hannes@xxxxxxxxxxx> Subject: mm: memcontrol: do not acquire page_cgroup lock for kmem pages Kmem page charging and uncharging is serialized by means of exclusive access to the page. Do not take the page_cgroup lock and don't set pc->flags atomically. Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxx> Acked-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Tejun Heo <tj@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/memcontrol.c | 21 +++++++-------------- 1 file changed, 7 insertions(+), 14 deletions(-) diff -puN mm/memcontrol.c~mm-memcontrol-do-not-acquire-page_cgroup-lock-for-kmem-pages mm/memcontrol.c --- a/mm/memcontrol.c~mm-memcontrol-do-not-acquire-page_cgroup-lock-for-kmem-pages +++ a/mm/memcontrol.c @@ -3458,12 +3458,13 @@ void __memcg_kmem_commit_charge(struct p memcg_uncharge_kmem(memcg, PAGE_SIZE << order); return; } - + /* + * The page is freshly allocated and not visible to any + * outside callers yet. Set up pc non-atomically. + */ pc = lookup_page_cgroup(page); - lock_page_cgroup(pc); pc->mem_cgroup = memcg; - SetPageCgroupUsed(pc); - unlock_page_cgroup(pc); + pc->flags = PCG_USED; } void __memcg_kmem_uncharge_pages(struct page *page, int order) @@ -3473,19 +3474,11 @@ void __memcg_kmem_uncharge_pages(struct pc = lookup_page_cgroup(page); - /* - * Fast unlocked return. Theoretically might have changed, have to - * check again after locking. - */ if (!PageCgroupUsed(pc)) return; - lock_page_cgroup(pc); - if (PageCgroupUsed(pc)) { - memcg = pc->mem_cgroup; - ClearPageCgroupUsed(pc); - } - unlock_page_cgroup(pc); + memcg = pc->mem_cgroup; + pc->flags = 0; /* * We trust that only if there is a memcg associated with the page, it _ Patches currently in -mm which might be from hannes@xxxxxxxxxxx are vmalloc-use-rcu-list-iterator-to-reduce-vmap_area_lock-contention.patch memcg-cleanup-memcg_cache_params-refcnt-usage.patch memcg-destroy-kmem-caches-when-last-slab-is-freed.patch memcg-mark-caches-that-belong-to-offline-memcgs-as-dead.patch slub-dont-fail-kmem_cache_shrink-if-slab-placement-optimization-fails.patch slub-make-slab_free-non-preemptable.patch memcg-wait-for-kfrees-to-finish-before-destroying-cache.patch slub-make-dead-memcg-caches-discard-free-slabs-immediately.patch slab-do-not-keep-free-objects-slabs-on-dead-memcg-caches.patch mm-memcontrol-fold-mem_cgroup_do_charge.patch mm-memcontrol-rearrange-charging-fast-path.patch mm-memcontrol-reclaim-at-least-once-for-__gfp_noretry.patch mm-huge_memory-use-gfp_transhuge-when-charging-huge-pages.patch mm-memcontrol-retry-reclaim-for-oom-disabled-and-__gfp_nofail-charges.patch mm-memcontrol-remove-explicit-oom-parameter-in-charge-path.patch mm-memcontrol-simplify-move-precharge-function.patch mm-memcontrol-catch-root-bypass-in-move-precharge.patch mm-memcontrol-use-root_mem_cgroup-res_counter.patch mm-memcontrol-remove-ordering-between-pc-mem_cgroup-and-pagecgroupused.patch mm-memcontrol-do-not-acquire-page_cgroup-lock-for-kmem-pages.patch mm-memcontrol-rewrite-charge-api.patch mm-memcontrol-rewrite-uncharge-api.patch memcg-deprecate-memoryforce_empty-knob.patch memcg-deprecate-memoryforce_empty-knob-fix.patch debugging-keep-track-of-page-owners.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html