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possible to throttle IO for svn clients?

From: Greg Barnett <gbarnett.lre_at_gmail.com>
Date: 2006-06-03 05:58:21 CEST

I'm having an issue where the disk IO from svn commands (most
noticeably update) is causing enough IOWAIT on RedHat Enterprise Linux
4 that other processes on the machine become unresponsive, and the
load climbs rapidly. Is there a way to throttle the amount of IO the
client uses? I'm OK with the command taking longer to run, if it
plays nicely with the other running processes.

The problem is worse on some machines than on others. On a dual
Opteron with SCSI HW Raid 5, it is annoying. On a single Pentium 4
with SATA SW Raid 1, it makes the server crawl until the command is

The repository currently contains about half a dozen websites (that
share many common elements), so there are quite a few largish binary
files, and very many websized images in addition to html pages and
code libraries. The repository is moderately large (nearly 800MB)
and will be growing to approximately 5GB as other related sites are

Things that I've tried to alleviate the situation:
Using the as, deadline and cfq kernel ioschedulers, with various
settings. The as scheduler with default settings seems to work the
best. I've been able to make the problem much worse with other

Making sure that the process is niced. Doesn't seem to control the IO
at all. I wanted to try ionice, but the RedHat Kernel doesn't support
ioprio_get, and due to things beyond my control, a newer kernel than
2.6.9 is not an option until RedHat upgrades the supplied kernel for

Preemptible kernel (2.6.9) didn't help.

Updating to subversion 1.3.2 didn't make any noticeable difference.

I've poked around the subversion source code a tiny bit with the idea
of putting a sleep call during or inbetween file writes, but the most
I've ever done in C is 'hello world', and that was ages ago, so I
didn't get too far there.

Removing some of the larger binary files such as movies from the
repository has helped, but I'd really prefer the repository to be an
accurate representation of the sites.

Any help would be greatly appreciated.


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Received on Sat Jun 3 11:56:07 2006

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