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Subject: Re: [RFC][PATCH] Reduce ext3 allocate-with-reservation lock
	latencies
From: Lee Revell <rlrevell@joe-job.com>
To: cmm@us.ibm.com
Cc: Andrew Morton <akpm@osdl.org>, "Stephen C. Tweedie" <sct@redhat.com>,
       Ingo Molnar <mingo@elte.hu>,
       linux-kernel <linux-kernel@vger.kernel.org>
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Date: Thu, 28 Apr 2005 12:12:05 -0400
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On Thu, 2005-04-28 at 00:37 -0700, Mingming Cao wrote:
> On Wed, 2005-04-27 at 23:45 -0400, Lee Revell wrote:
> > On Fri, 2005-04-22 at 15:10 -0700, Mingming Cao wrote:
> > > Please review. I have tested on fsx on SMP box. Lee, if you got time,
> > > please try this patch.
> > 
> > I have tested and this does fix the problem.  I ran my tests and no ext3
> > code paths showed up on the latency tracer at all, it never went above
> > 33 usecs.
> > 
> Thanks, Lee.
> 
> The patch survived on many fsx test over 20 hours on a 2cpu machine.
> Tested the patch on the same machine with tiobench (1-64 threads), and
> untar a kernel tree test, no regression there.
> However I see about 5-7% throughput drop on dbench with 16 threads. It
> probably due to the cpu cost that we have discussed.

Hmm, I guess someone needs to test it on a bigger system.  AFAICT this
should improve SMP scalability quite a bit.  Maybe that lock is rarely
contended.

Lee