[mythtv-users] pdflush is killing me

[Mark Lehrer]

On Tue, Feb 06, 2007 at 08:20:18AM +1100, Nick Tan wrote:

> According to the kernel documentation, pdflush periodically wakes up and 
> flushes old data to disk.  On one of my servers it was set to 5 seconds. 
>  Here's what I found in the kernel docs:

FYI, here is a cut & paste from another discussion about this; I
can't wait to get home and try it out:



> Experience with Ext3 data journaling indicates that dropping expire/writeback
> can help to smooth out I/O:
>
> vm.dirty_expire_centisecs = {300-1000}
> vm.dirty_writeback_centisecs = {50-100}
>

The performance limitation which is helped by tuning the VM to push
dirty pages earlier is in NFS not the underlying filesystem, so this
technique is useful with XFS too.



Mark