On Fri, 30 Mar 2007, Adam Borowski wrote:
> It's not that. It's /var/lib/dpkg/available.
>
> Try this:
>
> for x in /var/lib/apt/lists/*Packages;do dpkg --merge-avail "$x";done
> (or "dselect update")
> Install+purge of an empty package:
> 9-ish seconds on one box (my home desktop, years of use)
> 6-ish seconds on another (a slow server)
>
> dpkg --clear-avail
> Install+purge of an empty package:
> 0.182s on the slow server
> 3ish seconds on the desktop
>
> The difference between those 0.182s and 3s is due to removed and even purged
> packages staying in the available file.
Hmm. I've been wondering why upgrades seemed to take so long on my shiny
new desktop...
Here's a couple more data points for a 2GB/AMD64 box running 2.6.19.2 with
and ext3 filesystem. My test package was the sid/etch ethereal 'dummy'
package.
Original baseline:
% time (apt-get -y install ethereal && apt-get -y remove ethereal)
[ . . . ]
real 0m10.729s
user 0m6.692s
sys 0m1.224s
I threw out the first couple iterations after which these timings were
consistent to +- 0.1s across 5 subsequent samples.
Now, I blow away my (22 MB) /var/lib/dpkg/available file:
% dpkg --clear-avail
% time (apt-get -y install ethereal && apt-get -y remove ethereal)
[ . . . ]
real 0m6.492s
user 0m4.124s
sys 0m0.800s
I threw out the first couple iterations after which these timings were
consistent to +- 0.1s across 5 subsequent samples.
--> Result: 40% faster with an empty 'available' file.
On a whim I enabled dir_index on my ext3 FS, _and_ rebuilt info/:
% cd /var/lib/dpkg/
% cp -a info info.tmp
% mv info info.orig
% mv info.tmp info
I gather that should both defrag the info files (FWIW), and rebuild the
director using the hashed b-trees. (I don't see how the hashed b-trees
could impact this particular test, but what the hell...)
Then I redid the timing test:
%time (apt-get -y install ethereal && apt-get -y remove ethereal)
[ . . . ]
real 0m6.847s
user 0m4.100s
sys 0m0.776s
--> Result: No difference at all this time...
Then I replaced the 'available' file with an archived version and ran
the test again:
%time (apt-get -y install ethereal && apt-get -y remove ethereal)
[ . . . ]
real 0m10.869s
user 0m6.592s
sys 0m1.228s
--> Result: right back to the original (slow) baseline times
Looks like '/var/lib/dpkg/available' is the main culprit here. (I wish I
could test the same setup on a different filesystem like JFS though...)
-- Brad
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