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Date: Thu, 30 Apr 2009 09:20:58 -0400
From: "Alan D. Brunelle" <Alan.Brunelle@hp.com>
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To: Andrea Righi <righi.andrea@gmail.com>
CC: Paul Menage <menage@google.com>, Balbir Singh <balbir@linux.vnet.ibm.com>,
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Subject: Re: [PATCH 0/9] cgroup: io-throttle controller (v13)
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Hi Andrea -

FYI: I ran a simple test using this code to try and gauge the overhead
incurred by enabling this technology. Using a single 400GB volume split
into two 200GB partitions I ran two processes in parallel performing a
mkfs (ext2) on each partition. First w/out cgroup io-throttle and then
with it enabled (with each task having throttling enabled to
400MB/second (much, much more than the device is actually capable of
doing)). The idea here is to see the base overhead of just having the
io-throttle code in the paths.

Doing 30 runs of each (w/out & w/ io-throttle enabled) shows very little
difference (time in seconds)

w/out: min=80.196 avg=80.585 max=81.030 sdev=0.215 spread=0.834
with:  min=80.402 avg=80.836 max=81.623 sdev=0.327 spread=1.221

So only around 0.3% overhead - and that may not be conclusive with the
standard deviations seen.

--

FYI: The test was run on 2.6.30-rc1+your patches on a 16-way x86_64 box
(128GB RAM) plus a single FC volume off of a 1Gb FC RAID controller.

Regards,
Alan D. Brunelle
Hewlett-Packard