linux-kernel - Re: [PATCH 2/2] mm: warn about allocations which stall for too long

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Message-ID: <20160929091040.GE408@dhcp22.suse.cz>
Date:   Thu, 29 Sep 2016 11:10:40 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:     akpm@...ux-foundation.org, hannes@...xchg.org, mgorman@...e.de,
        dave.hansen@...el.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] mm: warn about allocations which stall for too long

On Thu 29-09-16 18:02:44, Tetsuo Handa wrote:
[...]
> > @@ -3650,6 +3652,14 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
> >  	if (order > PAGE_ALLOC_COSTLY_ORDER && !(gfp_mask & __GFP_REPEAT))
> >  		goto nopage;
> >  
> > +	/* Make sure we know about allocations which stall for too long */
> > +	if (time_after(jiffies, alloc_start + stall_timeout)) {
> > +		warn_alloc(gfp_mask,
> 
> I expect "gfp_mask & ~__GFP_NOWARN" rather than "gfp_mask" here.
> Otherwise, we can't get a clue for __GFP_NOWARN allocations.

If there is an explicit __GFP_NOWARN then I believe we should obey it
same way we do for the allocation failure. If you believe this is not
the best way then feel free to send a patch with an example where a
__GFP_NOWARN user would really like to see about the stall.
-- 
Michal Hocko
SUSE Labs