lkml.org 
[lkml]   [2004]   [Dec]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Prezeroing V2 [0/3]: Why and When it works


On Fri, 24 Dec 2004, Arjan van de Ven wrote:
>
> problem is.. will it buy you anything if you use the page again
> anyway... since such pages will be cold cached now. So for sure some of
> it is only shifting latency from kernel side to userspace side, but
> readprofile doesn't measure the later so it *looks* better...

Absolutely. I would want to see some real benchmarks before we do this.
Not just some microbenchmark of "how many page faults can we take without
_using_ the page at all".

I agree 100% with you that we shouldn't shift the costs around. Having a
hice hot-spot that we know about is a good thing, and it means that
performance profiles show what the time is really spent on. Often getting
rid of the hotspot just smears out the work over a wider area, making
other optimizations (like trying to make the memory footprint _smaller_
and removing the work entirely that way) totally impossible because now
the performance profile just has a constant background noise and you can't
tell what the real problem is.

Linus
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2009-11-18 23:46    [W:0.657 / U:0.812 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site