mm: memcg: remove optimization of keeping the root_mem_cgroup LRU lists empty (ad2b8e60) · Commits · 戴 / test

root_mem_cgroup, lacking a configurable limit, was never subject to limit reclaim, so the pages charged to it could be kept off its LRU lists. They would be found on the global per-zone LRU lists upon physical memory pressure and it made sense to avoid uselessly linking them to both lists. The global per-zone LRU lists are about to go away on memcg-enabled kernels, with all pages being exclusively linked to their respective per-memcg LRU lists. As a result, pages of the root_mem_cgroup must also be linked to its LRU lists again. This is purely about the LRU list, root_mem_cgroup is still not charged. The overhead is temporary until the double-LRU scheme is going away completely. Signed-off-by:

Johannes Weiner <jweiner@redhat.com> Reviewed-by:

KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Reviewed-by:

Michal Hocko <mhocko@suse.cz> Reviewed-by:

Kirill A. Shutemov <kirill@shutemov.name> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Cc: Balbir Singh <bsingharora@gmail.com> Cc: Ying Han <yinghan@google.com> Cc: Greg Thelen <gthelen@google.com> Cc: Michel Lespinasse <walken@google.com> Cc: Rik van Riel <riel@redhat.com> Cc: Minchan Kim <minchan.kim@gmail.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Hugh Dickins <hughd@google.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

+2 −10

Original line number	Diff line number	Diff line
		@@ -1031,8 +1031,6 @@ void mem_cgroup_del_lru_list(struct page *page, enum lru_list lru)
		mz = page_cgroup_zoneinfo(pc->mem_cgroup, page);
		/* huge page split is done under lru_lock. so, we have no races. */
		MEM_CGROUP_ZSTAT(mz, lru) -= 1 << compound_order(page);
		if (mem_cgroup_is_root(pc->mem_cgroup))
		return;
		VM_BUG_ON(list_empty(&pc->lru));
		list_del_init(&pc->lru);
		}
		@@ -1057,13 +1055,11 @@ void mem_cgroup_rotate_reclaimable_page(struct page *page)
		return;

		pc = lookup_page_cgroup(page);
		/* unused or root page is not rotated. */
		/* unused page is not rotated. */
		if (!PageCgroupUsed(pc))
		return;
		/* Ensure pc->mem_cgroup is visible after reading PCG_USED. */
		smp_rmb();
		if (mem_cgroup_is_root(pc->mem_cgroup))
		return;
		mz = page_cgroup_zoneinfo(pc->mem_cgroup, page);
		list_move_tail(&pc->lru, &mz->lists[lru]);
		}
		@@ -1077,13 +1073,11 @@ void mem_cgroup_rotate_lru_list(struct page *page, enum lru_list lru)
		return;

		pc = lookup_page_cgroup(page);
		/* unused or root page is not rotated. */
		/* unused page is not rotated. */
		if (!PageCgroupUsed(pc))
		return;
		/* Ensure pc->mem_cgroup is visible after reading PCG_USED. */
		smp_rmb();
		if (mem_cgroup_is_root(pc->mem_cgroup))
		return;
		mz = page_cgroup_zoneinfo(pc->mem_cgroup, page);
		list_move(&pc->lru, &mz->lists[lru]);
		}
		@@ -1115,8 +1109,6 @@ void mem_cgroup_add_lru_list(struct page *page, enum lru_list lru)
		/* huge page split is done under lru_lock. so, we have no races. */
		MEM_CGROUP_ZSTAT(mz, lru) += 1 << compound_order(page);
		SetPageCgroupAcctLRU(pc);
		if (mem_cgroup_is_root(pc->mem_cgroup))
		return;
		list_add(&pc->lru, &mz->lists[lru]);
		}

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