linux-kernel - Re: [PATCH] memcg, oom: no oom-kill for __GFP_RETRY

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Message-ID: <20190429122214.GK21837@dhcp22.suse.cz>
Date:   Mon, 29 Apr 2019 08:22:14 -0400
From:   Michal Hocko <mhocko@...nel.org>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>, linux-mm@...ck.org,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] memcg, oom: no oom-kill for __GFP_RETRY_MAYFAIL

On Sun 28-04-19 16:56:13, Shakeel Butt wrote:
> The documentation of __GFP_RETRY_MAYFAIL clearly mentioned that the
> OOM killer will not be triggered and indeed the page alloc does not
> invoke OOM killer for such allocations. However we do trigger memcg
> OOM killer for __GFP_RETRY_MAYFAIL. Fix that.

An example of __GFP_RETRY_MAYFAIL memcg OOM report would be nice. I
thought we haven't been using that flag for memcg allocations yet.
But this is definitely good to have addressed.

> Signed-off-by: Shakeel Butt <shakeelb@...gle.com>

Acked-by: Michal Hocko <mhocko@...e.com>

> ---
>  mm/memcontrol.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 2713b45ec3f0..99eca724ed3b 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2294,7 +2294,6 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
>  	unsigned long nr_reclaimed;
>  	bool may_swap = true;
>  	bool drained = false;
> -	bool oomed = false;
>  	enum oom_status oom_status;
>  
>  	if (mem_cgroup_is_root(memcg))
> @@ -2381,7 +2380,7 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
>  	if (nr_retries--)
>  		goto retry;
>  
> -	if (gfp_mask & __GFP_RETRY_MAYFAIL && oomed)
> +	if (gfp_mask & __GFP_RETRY_MAYFAIL)
>  		goto nomem;
>  
>  	if (gfp_mask & __GFP_NOFAIL)
> @@ -2400,7 +2399,6 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
>  	switch (oom_status) {
>  	case OOM_SUCCESS:
>  		nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
> -		oomed = true;
>  		goto retry;
>  	case OOM_FAILED:
>  		goto force;
> -- 
> 2.21.0.593.g511ec345e18-goog
> 

-- 
Michal Hocko
SUSE Labs