Commit 4c9c5359 authored Dec 18, 2012 by Suleiman Souhlal Committed by Linus Torvalds Dec 18, 2012

memcg: reclaim when more than one page needed



mem_cgroup_do_charge() was written before kmem accounting, and expects
three cases: being called for 1 page, being called for a stock of 32
pages, or being called for a hugepage.  If we call for 2 or 3 pages (and
both the stack and several slabs used in process creation are such, at
least with the debug options I had), it assumed it's being called for
stock and just retried without reclaiming.

Fix that by passing down a minsize argument in addition to the csize.

And what to do about that (csize == PAGE_SIZE && ret) retry?  If it's
needed at all (and presumably is since it's there, perhaps to handle
races), then it should be extended to more than PAGE_SIZE, yet how far?
And should there be a retry count limit, of what?  For now retry up to
COSTLY_ORDER (as page_alloc.c does) and make sure not to do it if
__GFP_NORETRY.

v4: fixed nr pages calculation pointed out by Christoph Lameter.

Signed-off-by: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Glauber Costa <glommer@parallels.com>
Acked-by: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Frederic Weisbecker <fweisbec@redhat.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: JoonSoo Kim <js1304@gmail.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent a0956d54

mm/memcontrol.c

+9 −7

Original line number	Diff line number	Diff line
		@@ -2258,7 +2258,8 @@ enum {
		};

		static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
		unsigned int nr_pages, bool oom_check)
		unsigned int nr_pages, unsigned int min_pages,
		bool oom_check)
		{
		unsigned long csize = nr_pages * PAGE_SIZE;
		struct mem_cgroup *mem_over_limit;
		@@ -2281,18 +2282,18 @@ static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
		} else
		mem_over_limit = mem_cgroup_from_res_counter(fail_res, res);
		/*
		* nr_pages can be either a huge page (HPAGE_PMD_NR), a batch
		* of regular pages (CHARGE_BATCH), or a single regular page (1).
		*
		* Never reclaim on behalf of optional batching, retry with a
		* single page instead.
		*/
		if (nr_pages == CHARGE_BATCH)
		if (nr_pages > min_pages)
		return CHARGE_RETRY;

		if (!(gfp_mask & __GFP_WAIT))
		return CHARGE_WOULDBLOCK;

		if (gfp_mask & __GFP_NORETRY)
		return CHARGE_NOMEM;

		ret = mem_cgroup_reclaim(mem_over_limit, gfp_mask, flags);
		if (mem_cgroup_margin(mem_over_limit) >= nr_pages)
		return CHARGE_RETRY;
		@@ -2305,7 +2306,7 @@ static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
		* unlikely to succeed so close to the limit, and we fall back
		* to regular pages anyway in case of failure.
		*/
		if (nr_pages == 1 && ret)
		if (nr_pages <= (1 << PAGE_ALLOC_COSTLY_ORDER) && ret)
		return CHARGE_RETRY;

		/*
		@@ -2439,7 +2440,8 @@ again:
		nr_oom_retries = MEM_CGROUP_RECLAIM_RETRIES;
		}

		ret = mem_cgroup_do_charge(memcg, gfp_mask, batch, oom_check);
		ret = mem_cgroup_do_charge(memcg, gfp_mask, batch, nr_pages,
		oom_check);
		switch (ret) {
		case CHARGE_OK:
		break;

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