Re: Per-file bandwidth requirements

From: Jens Axboe <>
Date: Mon, 17 Sep 2007 12:18:47 +0200

On Mon, Sep 17 2007, Joshua Root wrote:
> Carl Henrik Lunde wrote:
> > Hi!
> >
> > I would like to simulate a load with multiple files with different bandwidth
> > requirements in the same process:
> >
> > Process 1: file A: rate=10 MB/s, file B: rate=1 MB/s, file C: rate=idle
> > Process 2: file D: rate=20 MB/s, file E: rate=idle
> >
> > By "rate=idle" I mean that there should not be any IO unless all the other
> > rates specified in the process are met.
> >
> > As far as I can see this is not possible with the current version of fio?
> >
> You can set a job's priority to idle by setting prioclass=3. This would
> only work when using the CFQ I/O scheduler. I don't think there's any
> way to adjust the priority on a per-file basis.

I think Carl is asking about the fio rate feature, not kernel scheduler
priorities. Carl, you are correct in assuming that fio currently cannot
do what you describe. It's interesting though, I'll think about how I
can best support something like that. Perhaps just extending filename to
support it, ala


That is, support filename=filename/rate/type(or class) type styles so
you can customize the rate* settings on a per-file basis inside the job.

Let me consider it a bit :-)

Jens Axboe
Received on Mon Sep 17 2007 - 12:18:47 CEST

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