linux-kernel - Re: [PATCH v2] memcg: allow exiting tasks to write back data to swap

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Message-ID: <298822027ef468c290a67fe98e228348e2b389de.camel@surriel.com>
Date: Tue, 14 Jan 2025 11:56:47 -0500
From: Rik van Riel <riel@...riel.com>
To: Michal Hocko <mhocko@...e.com>, Johannes Weiner <hannes@...xchg.org>
Cc: Yosry Ahmed <yosryahmed@...gle.com>, Balbir Singh <balbirs@...dia.com>, 
 Roman Gushchin <roman.gushchin@...ux.dev>, hakeel Butt
 <shakeel.butt@...ux.dev>, Muchun Song	 <muchun.song@...ux.dev>, Andrew
 Morton <akpm@...ux-foundation.org>, 	cgroups@...r.kernel.org,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org, 	kernel-team@...a.com,
 Nhat Pham <nphamcs@...il.com>
Subject: Re: [PATCH v2] memcg: allow exiting tasks to write back data to swap

On Tue, 2025-01-14 at 17:54 +0100, Michal Hocko wrote:
> O
> Btw. is there any actual reason why we cannot go nomem without going
> to the oom killer (just to bail out) and go through the whole cycle
> again? That seems arbitrary and simply burning a lot of cycle without
> much chances to make any better outcome
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 7b3503d12aaf..eb45eaf0acfc 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2268,8 +2268,7 @@ int try_charge_memcg(struct mem_cgroup *memcg,
> gfp_t gfp_mask,
>  	if (gfp_mask & __GFP_RETRY_MAYFAIL)
>  		goto nomem;
>  
> -	/* Avoid endless loop for tasks bypassed by the oom killer
> */
> -	if (passed_oom && task_is_dying())
> +	if (task_is_dying())
>  		goto nomem;
>  
>  	/*

When we return from the page fault handler, we
restart the instruction that faulted.

That means we could just end up repeating the
same fault over and over again.

-- 
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