Thread (113 messages) 113 messages, 8 authors, 2012-08-22

Re: [PATCH v2 02/11] memcg: Reclaim when more than one page needed.

From: Michal Hocko <hidden>
Date: 2012-08-10 15:42:46
Also in: linux-mm, lkml

On Thu 09-08-12 17:01:10, Glauber Costa wrote:
[...]
quoted hunk ↗ jump to hunk
@@ -2317,18 +2318,18 @@ 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;
This is dangerous because THP charges will be retried now while they
previously failed with CHARGE_NOMEM which means that we will keep
attempting potentially endlessly.
Why cannot we simply do if (nr_pages < CHARGE_BATCH) and get rid of the
min_pages altogether?
Also the comment doesn't seem to be valid anymore.
quoted hunk ↗ jump to hunk
 
 	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;
@@ -2341,7 +2342,7 @@ 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;
 
 	/*
@@ -2476,7 +2477,8 @@ 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;
-- 
1.7.11.2

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-- 
Michal Hocko
SUSE Labs
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