Re: O(1) scheduler gives big boost to tbench 192

[Andrea Arcangeli <andrea@suse.de>]

On Mon, May 06, 2002 at 04:20:05AM -0400, rwhron@earthlink.net wrote:
> > BTW, Randy, I seen my tree runs slower with tiobench, that's probably
> > because I made the elevator anti-starvation logic more aggressive than
> > mainline and the other kernel trees (to help interactive usage), could
> > you try to run tiobench on -aa after elvtune -r 8192 -w 16384
> > /dev/hd[abcd] to verify? Thanks for the great benchmarking effort.
> 
> I will have results on the big machine in a couple days.  On the 
> small machine, elvtune increases tiobench sequential reads by
> 30-50%, and lowers worst case latency a little.

ok, everything is fine then, thanks for the further benchmarks. Not sure
if I should increase the elvtune defaults, the max latency with 8
reading threads literally doubles (from a mean of 500/600 to 1200). OTOH
with 128 threads max latency even decreases (most probably because of
higher mean throughput).

> > And for the reason fork is faster in -aa that's partly thanks to the
> > reschedule-child-first logic, that can be easily merged in mainline,
> > it's just in 2.5.
> 
> Is that part of parent_timeslice patch?  parent_timeslice helped 

Yep.

> fork a little when I tried to isolating patches to find what
> makes fork faster in -aa.  It is more than one patch as far as 
> I can tell.
> 
> On uniprocessor the unixbench execl test, all -aa kernel's going back 
> at least to 2.4.15aa1 are about 20% faster than other trees, even those 
> like jam and akpm's splitted vm.  Fork in -aa for more "real world" 
> test (autoconf build) is about 8-10% over other kernel trees.
> 
> On quad Xeon, with bigger L2 cache, autoconf (fork test) the difference
> between mainline and -aa is smaller.  The -aa based VMs in aa, jam, and
> mainline have about 15% edge over rmap VM in ac and rmap.  jam has a
> slight advantage for autoconf build, possibly because of O(1) effect
> which is more likely to show up since more processes execute
> on the 4 way box.
> 
> More quad Xeon at:
> http://home.earthlink.net/~rwhron/kernel/bigbox.html
> 
> 
> -- 
> Randy Hron


Andrea