linux-kernel - Re: [PATCH 8/8] Add VM counters for transparent hugepages

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Message-ID: <20110222164331.GA31195@random.random>
Date:	Tue, 22 Feb 2011 17:43:31 +0100
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	Dave Hansen <dave@...ux.vnet.ibm.com>
Cc:	Andi Kleen <andi@...stfloor.org>, akpm@...ux-foundation.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	lwoodman@...hat.com, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 8/8] Add VM counters for transparent hugepages

On Tue, Feb 22, 2011 at 08:36:26AM -0800, Dave Hansen wrote:
> On Mon, 2011-02-21 at 11:07 -0800, Andi Kleen wrote:
> > From: Andi Kleen <ak@...ux.intel.com>
> > 
> > I found it difficult to make sense of transparent huge pages without
> > having any counters for its actions. Add some counters to vmstat
> > for allocation of transparent hugepages and fallback to smaller
> > pages.
> > 
> > Optional patch, but useful for development and understanding the system.
> 
> Very nice.  I did the same thing, splits-only.  I also found this stuff
> a must-have for trying to do any work with transparent hugepages.  It's
> just impossible otherwise.

This patch is good too. 1 and 8 I think can go in, patch 1 is high
priority.

Patches 2-5 I've an hard time to see how they're not hurting
performance instead of improving it, especially patch 3 looks dead
wrong and has no chance by the very design of KSM and by the random
(vma-ignoring) NUMA affinity of PageKSM, patch 3 is most certainly a
regression.

Patch 6-7 I didn't evaluate those yet, they look good, even if low
priority.

Acked-by: Andrea Arcangeli <aarcange@...hat.com>

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