On Wed, 9 May 2007 16:10:05 -0700
"Yu, Fenghua" <[email protected]> wrote:
>
>
> On Wed, 9 May 2007, Andrew Morton wrote:
>
> >> erm, it's not obviosu from all this that the patches are worth
> proceeding
> >> with, are they?
>
> >What was it? 0.5% performance improvement on a synthetic benchmark?
> >Process wakeup I believe?
>
> The initial patch and discussion is from:
> http://www.uwsg.iu.edu/hypermail/linux/kernel/0704.1/0340.html
>
> Yes, the runqueue patch has a 0.5% perf improvement on database
> workload(which is a good improvement for this workload).
>
> The theory behind the patches is:
>
> 1. Minimize number of cache lines that are touched during a remote
> access. On Numa system, remote access is more expensive than local.
> 2. Do not share cache line between remote accessed data and local
> accessed data. Local data update may cause remote access cache miss and
> wait for longer time.
>
> Although the patches themselves don't save or waste per_cpu size, the
> above two reasons are good to have them in.
>
Guys, this is all a lesson in the value of changelogs, and in how not to
write them.
Can you please prepare a new changelog for these patches? Something which
encapsulates all the above in as brief a form as possible and which
includes some numbers describing the space and/or speed improvements?
Thanks.
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