The patch titled Subject: mm: memcontrol: remove ordering between pc->mem_cgroup and PageCgroupUsed has been removed from the -mm tree. Its filename was mm-memcontrol-remove-ordering-between-pc-mem_cgroup-and-pagecgroupused.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Johannes Weiner <hannes@xxxxxxxxxxx> Subject: mm: memcontrol: remove ordering between pc->mem_cgroup and PageCgroupUsed There is a write barrier between setting pc->mem_cgroup and PageCgroupUsed, which was added to allow LRU operations to lookup the memcg LRU list of a page without acquiring the page_cgroup lock. But ever since 38c5d72f3ebe ("memcg: simplify LRU handling by new rule"), pages are ensured to be off-LRU while charging, so nobody else is changing LRU state while pc->mem_cgroup is being written, and there are no read barriers anymore. Remove the unnecessary write barrier. Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Tejun Heo <tj@xxxxxxxxxx> Cc: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/memcontrol.c | 9 --------- 1 file changed, 9 deletions(-) diff -puN mm/memcontrol.c~mm-memcontrol-remove-ordering-between-pc-mem_cgroup-and-pagecgroupused mm/memcontrol.c --- a/mm/memcontrol.c~mm-memcontrol-remove-ordering-between-pc-mem_cgroup-and-pagecgroupused +++ a/mm/memcontrol.c @@ -2795,14 +2795,6 @@ static void __mem_cgroup_commit_charge(s } pc->mem_cgroup = memcg; - /* - * We access a page_cgroup asynchronously without lock_page_cgroup(). - * Especially when a page_cgroup is taken from a page, pc->mem_cgroup - * is accessed after testing USED bit. To make pc->mem_cgroup visible - * before USED bit, we need memory barrier here. - * See mem_cgroup_add_lru_list(), etc. - */ - smp_wmb(); SetPageCgroupUsed(pc); if (lrucare) { @@ -3483,7 +3475,6 @@ void mem_cgroup_split_huge_fixup(struct for (i = 1; i < HPAGE_PMD_NR; i++) { pc = head_pc + i; pc->mem_cgroup = memcg; - smp_wmb();/* see __commit_charge() */ pc->flags = head_pc->flags & ~PCGF_NOCOPY_AT_SPLIT; } __this_cpu_sub(memcg->stat->count[MEM_CGROUP_STAT_RSS_HUGE], _ Patches currently in -mm which might be from hannes@xxxxxxxxxxx are origin.patch mm-memcontrol-rewrite-charge-api.patch mm-memcontrol-rewrite-uncharge-api.patch mm-memcontrol-use-page-lists-for-uncharge-batching.patch mm-memcontrol-use-page-lists-for-uncharge-batching-fix-hugetlb-page-lru.patch page-cgroup-trivial-cleanup.patch page-cgroup-get-rid-of-nr_pcg_flags.patch memcg-remove-lookup_cgroup_page-prototype.patch mm-memcontrol-avoid-charge-statistics-churn-during-page-migration.patch nilfs2-integrate-sysfs-support-into-driver-fix.patch linux-next.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