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Re: Very aggressive memory reclaim

To: Andi Kleen <andi@xxxxxxxxxxxxxx>
Subject: Re: Very aggressive memory reclaim
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Tue, 29 Mar 2011 12:57:27 +1100
Cc: John Lepikhin <johnlepikhin@xxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, linux-mm@xxxxxxxxx
In-reply-to: <m2bp0u23wl.fsf@xxxxxxxxxxxxxx>
References: <AANLkTinFqqmE+fTMTLVU-_CwPE+LQv7CpXSQ5+CdAKLK@xxxxxxxxxxxxxx> <20110328215344.GC3008@dastard> <m2bp0u23wl.fsf@xxxxxxxxxxxxxx>
User-agent: Mutt/1.5.20 (2009-06-14)
On Mon, Mar 28, 2011 at 04:58:50PM -0700, Andi Kleen wrote:
> Dave Chinner <david@xxxxxxxxxxxxx> writes:
> >
> > First it would be useful to determine why the VM is reclaiming so
> > much memory. If it is somewhat predictable when the excessive
> > reclaim is going to happen, it might be worth capturing an event
> 
> Often it's to get pages of a higher order. Just tracing alloc_pages
> should tell you that.

Yes, the kmem/mm_page_alloc tracepoint gives us that. But in case
that is not the cause, grabbing all the trace points I suggested is
more likely to indicate where the problem is. I'd prefer to get more
data than needed the first time around than have to do multiple
round trips because a single trace point doesn't tell us the cause...

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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