linux-kernel - Re: [PATCH -v8][RFC] mutex: implement adaptive spinning

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Date:	Mon, 12 Jan 2009 12:30:12 -0500
From:	Chris Mason <chris.mason@...cle.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Gregory Haskins <ghaskins@...ell.com>,
	Matthew Wilcox <matthew@....cx>,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-btrfs <linux-btrfs@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Nick Piggin <npiggin@...e.de>,
	Peter Morreale <pmorreale@...ell.com>,
	Sven Dietrich <SDietrich@...ell.com>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>
Subject: Re: [PATCH -v8][RFC] mutex: implement adaptive spinning

On Mon, 2009-01-12 at 18:24 +0100, Peter Zijlstra wrote:
> On Mon, 2009-01-12 at 12:14 -0500, Chris Mason wrote:
> > On Mon, 2009-01-12 at 17:50 +0100, Peter Zijlstra wrote:
> > > > 
> > > > (the file stat run is total run time, so lower is better.  The other
> > > > numbers are files or MB per second, so higher is better)
> > > > 
> > > > For the file create run, v8 had much lower system time than v7,
> > > > averaging 1s of sys time per proc instead of 1.6s.
> > > 
> > > Right, how about the spread in completion time, because that is the only
> > > reason I tried this fairness stuff, because you reported massive
> > > differences there.
> > > 
> > 
> > I reran the numbers with a slightly different kernel config and they
> > have changed somewhat.  These are just for the 4k file create run, all
> > numbers in files created per second (and the numbers are stable across
> > runs)
> > 
> > v8 avg 176.90 median 171.85 std 12.49 high 215.97 low 165.54
> > v7 avg 169.02 median 163.77 std 16.82 high 267.95 low 157.95
> 
> Any opinions on the fairness matter, will -v9 be unlocked and unfair
> again?

I'd rather have it simple than fair.  My benchmarks are pretty dumb, I
wouldn't want to add complexity just based on them.

-chris




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