Re: multi-second freezes with current GIT?

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 08 May 2007 23:23:26 -0700 (PDT) David Miller <davem@davemloft.net> wrote:

> From: Mike Galbraith <efault@gmx.de>
> Date: Wed, 09 May 2007 05:29:20 +0200
> 
> > On Tue, 2007-05-08 at 18:44 -0700, David Miller wrote:
> > > I've been noticing this off and on for the past week or so.
> > > 
> > > The system seems to jam up for several seconds, anything that would
> > > need to read from disk just sits there during this time.  I think it's
> > > correlated with generating a lot of dirty write data.
> > > 
> > > My mouse moves around in X etc. so it really is only processes that
> > > need to read from disk that get stuck.
> > > 
> > > Perhaps it's a side effect of those dirty ratio changes Linus made to
> > > start off the 2.6.22 merge cycle?
> > 
> > Uhoh, that seems highly likely.
> > 
> > I think those changes may have been triggered by my repeatable and truly
> > horrible system stalls when writing to an ext3 data=ordered nearly full
> > filesystem.  Anything that does fdatasync() and/or fsync() can cause
> > very bad experiences indeed.  KDE's little menu/program launcher
> > doohickey does fdatasync() for some odd reason, which has utterly killed
> > my entire GUI for up to and including 20 minutes at a whack.
> > 
> > Switching to data=writeback cured those horrors.  Lowering the dirty
> > ratio reduced the agony of data=ordered tremendously, but didn't make it
> > even remotely acceptable.
> 
> I'm using data=ordered on my partitions too.


does

echo 40 > /proc/sys/vm/dirty_ratio
echo 10 > /proc/sys/vm/dirty_background_ratio

fix it?