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Re: How to handle TIF_MEMDIE stalls?

To: mhocko@xxxxxxx, hannes@xxxxxxxxxxx
Subject: Re: How to handle TIF_MEMDIE stalls?
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Date: Thu, 19 Feb 2015 22:29:37 +0900
Cc: david@xxxxxxxxxxxxx, dchinner@xxxxxxxxxx, linux-mm@xxxxxxxxx, rientjes@xxxxxxxxxx, oleg@xxxxxxxxxx, akpm@xxxxxxxxxxxxxxxxxxxx, mgorman@xxxxxxx, torvalds@xxxxxxxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, fernando_b1@xxxxxxxxxxxxx
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In-reply-to: <20150219122914.GH28427@xxxxxxxxxxxxxx>
References: <20150218082502.GA4478@xxxxxxxxxxxxxx> <20150218104859.GM12722@dastard> <20150218121602.GC4478@xxxxxxxxxxxxxx> <20150219110124.GC15569@xxxxxxxxxxxxxxxxxxxxxx> <20150219122914.GH28427@xxxxxxxxxxxxxx>
Michal Hocko wrote:
> On Thu 19-02-15 06:01:24, Johannes Weiner wrote:
> [...]
> > Preferrably, we'd get rid of all nofail allocations and replace them
> > with preallocated reserves.  But this is not going to happen anytime
> > soon, so what other option do we have than resolving this on the OOM
> > killer side?
> 
> As I've mentioned in other email, we might give GFP_NOFAIL allocator
> access to memory reserves (by giving it __GFP_HIGH). This is still not a
> 100% solution because reserves could get depleted but this risk is there
> even with multiple oom victims. I would still argue that this would be a
> better approach because selecting more victims might hit pathological
> case more easily (other victims might be blocked on the very same lock
> e.g.).
> 
Does "multiple OOM victims" mean "select next if first does not die"?
Then, I think my timeout patch 
http://marc.info/?l=linux-mm&m=142002495532320&w=2
does not deplete memory reserves. ;-)

If we change to permit invocation of the OOM killer for GFP_NOFS / GFP_NOIO,
those who do not want to fail (e.g. journal transaction) will start passing
__GFP_NOFAIL?

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