linux-kernel - Re: [PATCH] mm: terminate shrink

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Message-ID: <20171207095835.GE20234@dhcp22.suse.cz>
Date:   Thu, 7 Dec 2017 10:58:35 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     Suren Baghdasaryan <surenb@...gle.com>, akpm@...ux-foundation.org,
        hannes@...xchg.org, hillf.zj@...baba-inc.com, minchan@...nel.org,
        mgorman@...hsingularity.net, ying.huang@...el.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        timmurray@...gle.com, tkjos@...gle.com
Subject: Re: [PATCH] mm: terminate shrink_slab loop if signal is pending

On Thu 07-12-17 18:52:23, Sergey Senozhatsky wrote:
> On (12/06/17 11:20), Suren Baghdasaryan wrote:
> > Slab shrinkers can be quite time consuming and when signal
> > is pending they can delay handling of the signal. If fatal
> > signal is pending there is no point in shrinking that process
> > since it will be killed anyway. This change checks for pending
> > fatal signals inside shrink_slab loop and if one is detected
> > terminates this loop early.
> > 
> > Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
> > ---
> >  mm/vmscan.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index c02c850ea349..69296528ff33 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -486,6 +486,13 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
> >  			.memcg = memcg,
> >  		};
> >  
> > +		/*
> > +		 * We are about to die and free our memory.
> > +		 * Stop shrinking which might delay signal handling.
> > +		 */
> > +		if (unlikely(fatal_signal_pending(current))
> 
> -               if (unlikely(fatal_signal_pending(current))
> +               if (unlikely(fatal_signal_pending(current)))

Heh, well, spotted. This begs a question how this has been tested, if at
all?
-- 
Michal Hocko
SUSE Labs