Responsiveness testing through dpkg

Chow Loong Jin hyperair at ubuntu.com
Tue Apr 27 08:46:06 BST 2010


On Tuesday 27,April,2010 03:33 PM, Tim Gardner wrote:
> On 04/26/2010 10:45 PM, Chase Douglas wrote:
>> Hello all,
>>
>> I'm interested in doing some desktop responsiveness testing, and I've
>> found that when I have a large number of packages to install/update it
>> kills my desktop responsiveness not only during installation, but also
>> for quite a bit of time afterwards. Desktop responsiveness is a rather
>> nebulous issue, one that occurs in different situations on different
>> hardware in different ways. However, apt-get/dpkg seem to do a good
>> job of causing desktop slowdowns across many configurations :).
>>
>> What I would like to do is find a good test case I can run on bare
>> hardware (not in a VM with snapshot capabilities) that is
>> reproducible. I think doing a reinstallation of a set of packages, say
>> ubuntu-desktop, would work well. Is there a safe way to do this?
>>
>> Thanks
>>
>> -- Chase
>>
> 
> I think dpkg is triggering the fsync problem. Andy and Surbhi have some 
> information on that.

That would be during the installation. But Chase did mention that it affected
responsiveness for some time afterwards as well. I believe this could be due to
large amounts of memory being swapped out to cache the large amounts of reads
and writes that dpkg makes.

Another thing worth noting is dpkg's memory usage. It seems to take anywhere
between 100M and 300M of memory on my system, for *any* operation at all. That
is almost on par with the memory usage of a virtual machine capable of running
Windows XP. Truncating /var/lib/dpkg/available to 0 before any dpkg runs brings
the memory usage closer to 100M than 300M. In fact, I'm thinking of replacing
dpkg with a script that truncates this file to 0 before running the real dpkg.

> Have you considered generating some kind of steady state background load 
> using bonnie or stress? I'd think those kind of loads are more likely in 
> the real world, whereas the dpkg scenario is relatively rare for most folks.

That doesn't stop dpkg from messing up system responsiveness big time. I think
this issue should be looked into as well.

-- 
Kind regards,
Chow Loong Jin

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