lkml.org 
[lkml]   [2009]   [Dec]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH RFC] [X86] Compile Option Os versus O2 on latest x86 platform
On 12/01/2009 02:14 AM, Arjan van de Ven wrote:
> On Tue, 1 Dec 2009 16:54:04 +0800
> "Ma, Ling" <ling.ma@intel.com> wrote:
>
>> Hi Ingo
>>
>> Thanks for your correction, so we use perf stat --repeat 3 to test
>> volano, tbench, and kbuild, Because netperf has multiple items we may
>> send out later.
>
> a key question is.. how much more memory do you have free due to -Os?
> (because memory is cache is performance on a system level as well)
> and how much less icache pressure is there?
>

From the re-run, it sounds like the only test that actually shows a
significant difference is volano. From reading the numbers, it looks
like the improvements are almost exclusively in IPC i.e. better
scheduling -- all the other metrics are substantially worse; including a
10% increase in cache misses.

It would be interesting to see what functions are hot in volano. It
might very well be that we could get a boost without significantly bloat
the kernel as a whole by picking out a couple of hot object files and
compiling those with -O2 or -O3.

-hpa

--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.


\
 
 \ /
  Last update: 2009-12-01 17:19    [W:0.069 / U:0.076 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site