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Subject: Re: [PATCH 3/3]Subject: CFQ: add think time check for group
From: Shaohua Li <shaohua.li@intel.com>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: lkml <linux-kernel@vger.kernel.org>, Jens Axboe <jaxboe@fusionio.com>
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Date: Thu, 07 Jul 2011 14:08:21 +0800
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On Wed, 2011-07-06 at 23:06 +0800, Vivek Goyal wrote:
> On Wed, Jul 06, 2011 at 09:58:40AM +0800, Shaohua Li wrote:
> [..]
> > > > [global]
> > > > runtime=30
> > > > direct=1
> > > > 
> > > > [test1]
> > > > cgroup=test1
> > > > cgroup_weight=1000
> > > > rw=randread
> > > > ioengine=libaio
> > > > size=500m
> > > > runtime=30
> > > > directory=/mnt
> > > > filename=file1
> > > > thinktime=9000
> > > > 
> > > > [test2]
> > > > cgroup=test2
> > > > cgroup_weight=1000
> > > > rw=randread
> > > > ioengine=libaio
> > > > size=500m
> > > > runtime=30
> > > > directory=/mnt
> > > > filename=file2
> > > > 
> > > > 	patched		base
> > > > test1	64k		39k
> > > > test2	540k		540k
> > > > total	604k		578k
> > > > 
> > > > group1 gets much better throughput because it waits less time.
> 
> I don't understand it. Thinktime of group test1 is more than 8ms. So now
> we should not be idling on test1. Hence test1 should lose some share and
> test2 should gain disk share and overall throughput should go up.
> 
> I am wondering why throughput of test2 did not go up?
hmm, actually the throughput of test2 is better. Maybe I wrote it down wrong.
test2 throughput is about 548k/s. Sorry.

> Also can you run some tests to make sure that disk shares of regular
> workloads (thinktime less than 8ms) are not impacted.
I tried think time 2ms or no think time. there is no difference. the
result is quite stable.

Thanks,
Shaohua