Michal Hocko Messages: 109 Registered: December 2011
Senior Member
On Sat 11-08-12 01:49:25, KAMEZAWA Hiroyuki wrote:
> (2012/08/11 0:42), Michal Hocko wrote:
> >On Thu 09-08-12 17:01:10, Glauber Costa wrote:
> >[...]
> >>@@ -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.
>
> with THP, I thought nr_pages == min_pages, and no retry.
right you are.
> >Why cannot we simply do if (nr_pages < CHARGE_BATCH) and get rid of the
> >min_pages altogether?
>
> Hm, I think a slab can be larger than CHARGE_BATCH.
>
> >Also the comment doesn't seem to be valid anymore.
> >
> I agree it's not clean. Because our assumption on nr_pages are changed,
> I think this behavior should not depend on nr_pages value..
> Shouldn't we have a flag to indicate "trial-for-batched charge" ?
dunno, it would require a new parameter anyway (because abusing gfp
doesn't seem great idea).
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