Re: ext3 performance inconsistencies, 2.4/2.6

From: Paul Venezia
Date: Tue Nov 04 2003 - 16:08:50 EST

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:

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.


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