linux-kernel - Re: [patch 21/21] slab defrag: Obsolete SLAB

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Date:	Fri, 16 May 2008 12:06:47 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Matthew Wilcox <matthew@....cx>
cc:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	Andi Kleen <andi@...stfloor.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Mel Gorman <mel@...net.ie>, mpm@...enic.com
Subject: Re: [patch 21/21] slab defrag: Obsolete SLAB

On Thu, 15 May 2008, Matthew Wilcox wrote:

> On Thu, May 15, 2008 at 12:09:06PM -0700, Christoph Lameter wrote:
> > Assumptions may be the issue. My own "reproducer" for remote frees is 
> > available from my git tree and I usually prefer to run my own. We 
> 
> No doubt you prefer to run a test which fails to show a problem with
> your code.  How about you try running a test which does show a problem?

The test was designed to show the worst case effect of the additional 
atomic op and it does its job. Look at the tests branch of my vm git tree.

> > There is no way of zeroing the counters. Run slabinfo -AD after the 
> > test application has been running for awhile. If you want a differential 
> > then you have to take two datapoints.
> 
> Is a differential interesting to you?

Depends on how much other stuff is going on before.

> 
> > > Otherwise I'll get something wrong and these numbers will be useless to
> > > you.  Or that's what you'll claim anyway.
> > 
> > No. I guess I will end up with a lot of guess work of what is going on on 
> > the system since the information is limited for some reason.
> 
> They're your statistics.  Tell me what you need.

The output of slabinfo -AD.... 


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