Re: Report: 2.4.18 very high latencies (with lowlat. and pre-empt patches)

[Andrew Morton <akpm@zip.com.au>]

Ricardo Galli wrote:
> 
> Hi all (second try),
>         Linux becomes somehow unusable when I edited sound files and also
> during NFS copy. I've noticed the same effects also during i/o loads, for
> example when closing kmail after I deleted some messages.
> 

It would help if you could come up with a simple test case
which exhibits this problem - some sequence of steps which
is reproducible by others, and which has repeatable effects.

Is your I/O system performing properly?  Try running

	hdparm -t /dev/hdaX

where /dev/hdaX refers to your root filesystem.  You
should get 15-30 megabytes per second.

You also report that your PPC-based laptop has processes
unexpectedly terminating when the machine is under VM
pressure.  You should check your kernel logs (usually
/var/log/messages) to see if the process was killed
due to an out-of-memory condition.  If it's not that,
and if it's not due to application bugs then the ppc
kernel may be dropping modified- or dirty-bits in its
PTEs, which is rather unlikely.

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