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SubjectRe: [PATCH 02/11] memcg: Reclaim when more than one page needed.
On Mon, 25 Jun 2012, Glauber Costa wrote:

> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 9304db2..8e601e8 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2158,8 +2158,16 @@ enum {
> CHARGE_OOM_DIE, /* the current is killed because of OOM */
> };
>
> +/*
> + * We need a number that is small enough to be likely to have been
> + * reclaimed even under pressure, but not too big to trigger unnecessary

Whitespace.

> + * retries
> + */
> +#define NR_PAGES_TO_RETRY 2
> +

Should be 1 << PAGE_ALLOC_COSTLY_ORDER? Where does this number come from?
The changelog doesn't specify.

> 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;
> @@ -2182,18 +2190,18 @@ 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;
> @@ -2206,7 +2214,7 @@ 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 <= NR_PAGES_TO_RETRY && ret)
> return CHARGE_RETRY;
>
> /*
> @@ -2341,7 +2349,8 @@ 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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