On Thu 29-05-14 12:15:55, Johannes Weiner wrote:
> There is no reason why oom-disabled and __GFP_NOFAIL charges should
> try to reclaim only once when every other charge tries several times
> before giving up. Make them all retry the same number of times.
I have mentioned that already with the last iteration of the patch.
This can make THP charges stall unnecessarily when the allocation could
fall back to single page charges.
MEM_CGROUP_RECLAIM_RETRIES * SWAP_CLUSTER_MAX + CHARGE_BATCH * CPUS
reclaimed pages will not help for huge pages so multiple reclaims is
just pointless waisting of time.
I think you should just move the next patch in the series up and simply make
the thp charge __GFP_NORETRY:
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b3a6deed66d5..ba822c27a55b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3703,10 +3703,13 @@ int mem_cgroup_charge_anon(struct page *page,
nr_pages <<= compound_order(page);
VM_BUG_ON_PAGE(!PageTransHuge(page), page);
/*
- * Never OOM-kill a process for a huge page. The
- * fault handler will fall back to regular pages.
+ * Never OOM-kill a process for a huge page. Also do not
+ * reclaim memcg too much because it wouldn't help the
+ * huge page charge anyway.
+ * The fault handler will fall back to regular pages.
*/
oom = false;
+ gfp_mask |= __GFP_NORETRY;
}
memcg = mem_cgroup_try_charge_mm(mm, gfp_mask, nr_pages, oom);
> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> ---
> mm/memcontrol.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 46b3e37542ad..e8d5075c081f 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2567,7 +2567,7 @@ static int mem_cgroup_try_charge(struct mem_cgroup *memcg,
> bool oom)
> {
> unsigned int batch = max(CHARGE_BATCH, nr_pages);
> - int nr_oom_retries = MEM_CGROUP_RECLAIM_RETRIES;
> + int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
> struct mem_cgroup *mem_over_limit;
> struct res_counter *fail_res;
> unsigned long nr_reclaimed;
> @@ -2639,6 +2639,9 @@ retry:
> if (mem_cgroup_wait_acct_move(mem_over_limit))
> goto retry;
>
> + if (nr_retries--)
> + goto retry;
> +
> if (gfp_mask & __GFP_NOFAIL)
> goto bypass;
>
> @@ -2648,9 +2651,6 @@ retry:
> if (!oom)
> goto nomem;
>
> - if (nr_oom_retries--)
> - goto retry;
> -
> mem_cgroup_oom(mem_over_limit, gfp_mask, get_order(batch));
> nomem:
> if (!(gfp_mask & __GFP_NOFAIL))
> --
> 1.9.3
>
--
Michal Hocko
SUSE Labs
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