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Date: Tue, 18 Oct 2016 17:02:43 +0200
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: mmap_sem bottleneck
Message-ID: <20161018150243.GZ3117@twins.programming.kicks-ass.net>
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To: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Cc: Linux MM <linux-mm@kvack.org>, Andi Kleen <ak@linux.intel.com>, Mel Gorman <mgorman@techsingularity.net>, Jan Kara <jack@suse.cz>, Michal Hocko <mhocko@suse.com>, Davidlohr Bueso <dbueso@suse.de>, Hugh Dickins <hughd@google.com>, Andrew Morton <akpm@linux-foundation.org>, Al Viro <viro@ZenIV.linux.org.uk>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

On Tue, Oct 18, 2016 at 04:50:10PM +0200, Laurent Dufour wrote:
> On 17/10/2016 14:51, Peter Zijlstra wrote:

> > Latest version is here:
> > 
> >   https://lkml.kernel.org/r/20141020215633.717315139@infradead.org
> > 
> > Plenty of bits left to sort with that, but the general idea is to use
> > the split page-table locks (PTLs) as range lock for the mmap_sem.
> 
> Thanks Peter for the pointer,
> 
> It sounds that some parts of this series are already upstream, like the
> use of the fault_env structure,

Right, Kirill picked that up.

> but the rest of the code need some
> refresh to apply on the latest kernel. I'll try to update your series
> and will give it a try asap.
> 
> This being said, I'm wondering if the concern Kirill raised about the
> VMA sequence count handling are still valid...

Yes, I think they are. I don't think I put much time into it after that
exchange :-(

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