Re: Linux 2.6.29

Alan Cox
2009-03-24T09:15:47Z

> posted to the list earlier trying to see if there was anything that
> could be done to help my specific case. I've got a system where if
> someone starts writing out a large file, it kills client NFS writes.
> Makes the system unusable:
> http://marc.info/?l=linux-kernel&m=123732127919368&w=2

I have not had this problem since I applied Arjan's (for some reason
repeatedly rejected) patch to change the ioprio of the various writeback
daemons. Under some loads changing to the noop I/O scheduler also seems
to help (as do most of the non default ones)

> Everyone seems to agree that "autotuning" it is the way to go. But no
> one seems willing to step up and try to do it. Probably because it's
> hard to get right!

If this is a VM problem why does fixing the I/O priority of the various
daemons seem to cure at least some of it ?

Alan