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SubjectRe: ext3 performance inconsistencies, 2.4/2.6

On Tue, 4 Nov 2003, Bill Rugolsky Jr. wrote:
>
> Well, I'm too lazy to wait for a long test, but with a mere
> 100MB file, on 1GHz P3:
>
> Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
> -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
> NPTL 100M 7735 99 127068 98 63048 84 7890 98 +++++ +++ +++++ +++
> LinuxThreads 100M 11000 99 127928 97 59075 84 11290 98 +++++ +++ +++++ +++
>
> So something is amiss.

Ok, so NPTL locking (even in the absense of any threads and thus any
contention) seems to be noticeably higher-overhead than the old
LinuxThreads.

90% of the overhead of a putc()/getc() implementation these days is likely
just locking. Even so, this implies that NPTL locking is about twice as
expensive as the old LinuxThreads one.

Don't ask me why. But I'm cc'ing Uli, who can probably tell us. Maybe the
RH-9 libraries are just not very good, and LinuxThreads has had a lot
longer to optimize their lock behaviour..

Linus


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