Re: ext3 performance inconsistencies, 2.4/2.6

From: Linus Torvalds
Date: Tue Nov 04 2003 - 15:34:35 EST

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

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.

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

That would be interesting.


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