linux-kernel - Re: [patch 08/12] mm: page_alloc: wait for OOM killer progress before retrying

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Message-ID: <20150326143223.GM15257@dhcp22.suse.cz>
Date:	Thu, 26 Mar 2015 15:32:23 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, ying.huang@...el.com,
	aarcange@...hat.com, david@...morbit.com, tytso@....edu
Subject: Re: [patch 08/12] mm: page_alloc: wait for OOM killer progress
 before retrying

On Thu 26-03-15 07:24:45, Johannes Weiner wrote:
> On Wed, Mar 25, 2015 at 11:15:48PM +0900, Tetsuo Handa wrote:
> > Johannes Weiner wrote:
[...]
> > >  	/*
> > > -	 * Acquire the oom lock.  If that fails, somebody else is
> > > -	 * making progress for us.
> > > +	 * This allocating task can become the OOM victim itself at
> > > +	 * any point before acquiring the lock.  In that case, exit
> > > +	 * quickly and don't block on the lock held by another task
> > > +	 * waiting for us to exit.
> > >  	 */
> > > -	if (!mutex_trylock(&oom_lock)) {
> > > -		*did_some_progress = 1;
> > > -		schedule_timeout_uninterruptible(1);
> > > -		return NULL;
> > > +	if (test_thread_flag(TIF_MEMDIE) || mutex_lock_killable(&oom_lock)) {
> > > +		alloc_flags |= ALLOC_NO_WATERMARKS;
> > > +		goto alloc;
> > >  	}
> > 
> > When a thread group has 1000 threads and most of them are doing memory allocation
> > request, all of them will get fatal_signal_pending() == true when one of them are
> > chosen by OOM killer.
> > This code will allow most of them to access memory reserves, won't it?
> 
> Ah, good point!  Only TIF_MEMDIE should get reserve access, not just
> any dying thread.  Thanks, I'll fix it in v2.

Do you plan to post this v2 here for review?

[...]
-- 
Michal Hocko
SUSE Labs
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