lkml.org 
[lkml]   [2002]   [Jan]   [12]   [last100]   RSS Feed
Views: [more markup]   [less markup]   [headers]   [forward]  
 
Messages in this thread
/
SubjectRe: [2.4.17/18pre] VM and swap - it's really unusable
FromRobert Love <>
Date12 Jan 2002 01:01:39 -0500
On Fri, 2002-01-11 at 15:22, Rob Landley wrote:

> So the best approach is a combination of the two patches.  SMP-on-UP for 
> everything outside of spinlocks, and then manually yielding locks that cause 
> problems.  Both Robert Love and Andrew Morton have come out in favor of each 
> other's patches on lkml just in the past few days.  The patches work together 
> quite well, and each wants to see the other's patch applied.

Right.  Here is what I want for 2.5 as a _general_ step towards a better
kernel that will yield better performance:

Merge the preemptible kernel patch.  A version is now out for
2.5.2-pre11 with support for Ingo's scheduler:

	ftp://ftp.kernel.org/pub/linux/kernel/people/rml/preempt-kernel

Next, make available a tool for profiling kernel latencies.  I have one
available now, preempt-stats, at the above url.  Andrew has some
excellent tools available at his website, too.  Something like this
could even be merged.  Daniel Phillips suggested a passive tool on IRC. 
Preempt-stats works like this.  It is off-by-default and, when enabled,
measures time between lock and unlock, reporting the top 20 worst-cases.

Begin working on the worst-case locks.  Solutions like Andrew's
low-latency and my lock-break are a start.  Better (at least in general)
solutions are to analyze the locks.  Localize them; make them finer
grained.  Analyze the algorithms.  Find the big problems.  Anyone look
at the tty layer lately?  Ugh.  Using the preemptive kernel as a base
and the analysis of the locks as a list of culprits, clean this cruft
up.  This would benefit SMP, too.  Perhaps a better locking construct is
useful.

The immediate result is good; the future is better.

	Robert Love

-
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: 2005-03-22 11:15    [from the cache]
©2003-2008