Subject: Re: ext3 performance inconsistencies, 2.4/2.6
From: Paul Venezia <pvenezia@jpj.net>
To: Linus Torvalds <torvalds@osdl.org>
Cc: "Bill Rugolsky Jr." <brugolsky@telemetry-investments.com>,
       linux-kernel@vger.kernel.org
In-Reply-To: <Pine.LNX.4.44.0311041227180.20373-100000@home.osdl.org>
References: <Pine.LNX.4.44.0311041227180.20373-100000@home.osdl.org>
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Date: Tue, 04 Nov 2003 16:07:43 -0500
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On Tue, 2003-11-04 at 15:30, Linus Torvalds wrote:
> On Tue, 4 Nov 2003, Bill Rugolsky Jr. wrote:
> > 
> > Unless bonnie++ is using the _unlocked() variants, it might be an issue of
> > the mutex overhead from NPTL v. LinuxThreads.  Red Hat 9 has its share
> > of NPTL bugs.
> 
> Hmm.. That would easily explain the differences, since NPTL will trigger 
> both on 2.6.0 and the RH-2.4 kernel, but not on the standard 2.4.22 
> kernel.
> 
> But there really should be zero contention on the stdio data structures, 
> so the locking would have to be _seriously_ broken to make that kind o 
> fdifference (not necessarily buggy, but seriously badly implemented). 
> 
> A non-contended lock should be at most one locked instruction if well 
> done, both on LinuxThreads and NPTL.

Good point... 

A truncated strace under 2.4.22 is here:
http://groove.jpj.net/bonnie-strace-trunc

It's incomplete, but shows the putc calls.

> > It is probably worth rerunning the tests with LD_ASSUME_KERNEL=2.4.1 on
> > the Red Hat kernel.
> 
> That would be interesting.

Tests are running now. Updates as events warrant.

-Paul

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