Re: Linux I/O tuning: CFQ vs. deadline

On Feb 10, 2010, at 1:37 AM, Greg Smith wrote:

> Jeff wrote:
>> I'd done some testing a while ago on the schedulers and at the time
>> deadline or noop smashed cfq.  Now, it is 100% possible since then
>> that they've made vast improvements to cfq and or the VM to get
>> better or similar performance.  I recall a vintage of 2.6 where
>> they severely messed up the VM. Glad I didn't upgrade to that one :)
>>
>> Here's the old post: http://archives.postgresql.org/pgsql-performance/2008-04/msg00155.php
>
> pgiosim doesn't really mix writes into there though, does it?  The
> mixed read/write situations are the ones where the scheduler stuff
> gets messy.
>

It has the abillity to rewrite blocks randomly as well - but I
honestly don't remember if I did that during my cfq/deadline test.
I'd wager I didn't.  Maybe I'll get some time to run some more tests
on it in the next couple days

> --
> Greg Smith    2ndQuadrant   Baltimore, MD
> PostgreSQL Training, Services and Support
> greg@2ndQuadrant.com  www.2ndQuadrant.com
>

--
Jeff Trout <jeff@jefftrout.com>
http://www.stuarthamm.net/
http://www.dellsmartexitin.com/