[mythtv-users] pdflush is killing me

Mark Lehrer mark at knm.org
Tue Feb 6 00:21:25 UTC 2007

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.


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