Date: Sun, 13 Jan 2008 10:16:07 +0530
From: Balbir Singh <balbir@linux.vnet.ibm.com>
To: Andrea Righi <righiandr@users.sourceforge.net>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>, Valdis.Kletnieks@vt.edu,
       LKML <linux-kernel@vger.kernel.org>, Jens Axboe <jens.axboe@oracle.com>
Subject: Re: [RFC][PATCH] per-task I/O throttling
Message-ID: <20080113044607.GA13633@balbir.in.ibm.com>
Reply-To: balbir@linux.vnet.ibm.com
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	Peter Zijlstra <a.p.zijlstra@chello.nl>, Valdis.Kletnieks@vt.edu,
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	Jens Axboe <jens.axboe@oracle.com>
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* Andrea Righi <righiandr@users.sourceforge.net> [2008-01-12 19:01:14]:

> Peter Zijlstra wrote:
> > On Sat, 2008-01-12 at 16:27 +0530, Balbir Singh wrote:
> >> * Peter Zijlstra <a.p.zijlstra@chello.nl> [2008-01-12 10:46:37]:
> >>
> >>> On Fri, 2008-01-11 at 23:57 -0500, Valdis.Kletnieks@vt.edu wrote:
> >>>> On Fri, 11 Jan 2008 17:32:49 +0100, Andrea Righi said:
> >>>>
> >>>>> The interesting feature is that it allows to set a priority for each
> >>>>> process container, but AFAIK it doesn't allow to "partition" the
> >>>>> bandwidth between different containers (that would be a nice feature
> >>>>> IMHO). For example it would be great to be able to define per-container
> >>>>> limits, like assign 10MB/s for processes in container A, 30MB/s to
> >>>>> container B, 20MB/s to container C, etc.
> >>>> Has anybody considered allocating based on *seeks* rather than bytes moved,
> >>>> or counting seeks as "virtual bytes" for the purposes of accounting (if the
> >>>> disk can do 50mbytes/sec, and a seek takes 5millisecs, then count it as 100K
> >>>> of data)?
> >>> I was considering a time scheduler, you can fill your time slot with
> >>> seeks or data, it might be what CFQ does, but I've never even read the
> >>> code.
> >>>
> >> So far the definition of I/O bandwidth has been w.r.t time. Not all IO
> >> devices have sectors; I'd prefer bytes over a period of time.
> > 
> > Doing a time based one would only require knowing the (avg) delay of
> > seeks, whereas doing a bytes based one would also require knowing the
> > (avg) speed of the device.
> > 
> > That is, if you're also interested in providing a latency guarantee.
> > Because that'd force you to convert bytes to time again.
> 
> So, what about considering both bytes/sec and io-operations/sec? In this
> way we should be able to limit huge streams of data and seek storms (or
> any mix of them).
> 
> Regarding CFQ, AFAIK it's only possible to configure an I/O priorty for
> a process, but there's no way for example to limit the bandwidth (or I/O
> operations/sec) for a particular user or group.
> 

Limiting usage is also a very useful feature. Andrea could you please
port your patches over to control groups.

-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL
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