[CentOS] Control IO related to a process

Martyn Hare martyn.hare at gmx.co.uk
Tue Sep 2 19:11:57 UTC 2008


On Tue, 2 Sep 2008 10:21:31 -0700
MHR <mhullrich at gmail.com> wrote:

> On Tue, Sep 2, 2008 at 9:51 AM, Joseph L. Casale
> <JCasale at activenetwerx.com> wrote:
> >
> > Appreciate that info, I have just been reading about the difference but
> > cant say I understand in real life what the difference between deadline
> > versus cfq is. I will try changing it on the fly and running my tests.
> >
> 
> The CFQ elevator algorithm attempts to be fair to all i/o requests,
> without specific regard to performance.  The deadline elevator is more
> aggressive in scheduling for minimal latency per device.
> 
> For example, if you have one process that is doing more or less random
> i/o and another that is doing large block sequential i/o, the deadline
> elevator will pander to the latter whereas the cfq elevator will try
> to be fair in scheduling the i/os between the processes.
> 
> Here's a decent, short write up on them:
> http://www.redhat.com/magazine/008jun05/features/schedulers/
> 
> HTH
> 
> mhr
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ionice?  has nobidy mentioned this?

-- 
Martyn Hare <martyn.hare at gmx.co.uk>
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