lkml.org 
[lkml]   [2015]   [Feb]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC PATCH] x86, fpu: Use eagerfpu by default on all CPUs

* Ingo Molnar <mingo@kernel.org> wrote:

> - Do you have enough RAM that there's essentially no IO
> in the system worth speaking of? Do you have enough RAM
> to copy a whole kernel tree to /tmp/linux/ and do the
> measurement there, on ramfs?

Doing that will also pin down the page cache: kernel build
times are very sensitive to the page cache layout, and once
a page cache layout is established on systems with lots of
RAM it does not tend to be flushed out. But the next bootup
will generate another random page cache layout - which
makes inter-kernel kernel build times comparisons much
noiser than the run-to-run numbers suggest.

So to get more precise measurements a 'pinned' page cache
layout and the dynamic debug switch you implemented is very
helpful and --repeat stddev will be pretty representative
of the true noise of the measurement.

Thanks,

Ingo


\
 
 \ /
  Last update: 2015-02-22 09:41    [W:0.101 / U:0.348 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site