Message-ID: <47055F84.109@redhat.com>
Date: Thu, 04 Oct 2007 17:47:48 -0400
From: Chuck Ebbert <cebbert@redhat.com>
Organization: Red Hat
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To: David Miller <davem@davemloft.net>
CC: willy@linux.intel.com, clameter@sgi.com, nickpiggin@yahoo.com.au,
       hch@lst.de, mel@skynet.ie, linux-fsdevel@vger.kernel.org,
       linux-kernel@vger.kernel.org, dgc@sgi.com, jens.axboe@oracle.com,
       suresh.b.siddha@intel.com
Subject: Re: SLUB performance regression vs SLAB
References: <20071004192824.GA9852@linux.intel.com>	<20071004.135537.39158051.davem@davemloft.net>	<470554D9.2050505@redhat.com> <20071004.141113.08322956.davem@davemloft.net>
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On 10/04/2007 05:11 PM, David Miller wrote:
> From: Chuck Ebbert <cebbert@redhat.com>
> Date: Thu, 04 Oct 2007 17:02:17 -0400
> 
>> How do you simulate reading 100TB of data spread across 3000 disks,
>> selecting 10% of it using some criterion, then sorting and
>> summarizing the result?
> 
> You repeatedly read zeros from a smaller disk into the same amount of
> memory, and sort that as if it were real data instead.

You've just replaced 3000 concurrent streams of data with a single
stream.  That won't test the memory allocator's ability to allocate
memory to many concurrent users very well.
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