Re: 2.4.19pre9aa2

[Andrea Arcangeli <andrea@suse.de>]

On Mon, Jun 03, 2002 at 08:15:05AM -0400, rwhron@earthlink.net wrote:
> More benchmarks on quad Xeon at:
> http://home.earthlink.net/~rwhron/kernel/bigbox.html

very cool work as usual :). Many thanks.

Just a note, watch the "File & VM system latencies in microseconds"
lmbench results, the creat become significantly slower, I'm wondering if
that's due the removal of the negative dcache after unlink. I think it's
still a global optimization (infact I think some of the dbench records
are also thanks to maximzing the useful cache information by dropping
immediatly negative dentries after unlink), but I wonder if the
benchmark is done in a way that generate false positives. To avoid false
positives and to really benchmark the whole "creat" path (that includes
in its non-cached form also a lookup in the lowlevel fs) lmbench should
rmdir; mkdir the directory where it wants to make the later creats
(rmdir/mkdir cycle will drop negative dentries in all 2.[245] kernels
too).  Otherwise at the moment I'm unsure what made creat slower between
pre8aa3 and pre9aa2, could it be a fake result of the benchmark? Maybe
you could give it a second spin just in case. The pipe bandwith reported
by lmbench in pre9aa2 is also very impressive, that's Mike's patch and I
think it's also a very worthwhile optimizations since many tasks really
uses pipes to passthrough big loads of data.

Andrea