Am Donnerstag, den 07.06.2012, 06:59 +0200 schrieb Guillem Jover: > Hi! > > On Thu, 2012-06-07 at 01:25:07 +0200, Benjamin Drung wrote: > > Package: dpkg-dev > > Version: 1.16.1.2ubuntu7 > > Severity: normal > > File: /usr/bin/dpkg-vendor > > > dpkg-vendor is small useful program that is used by different other > > programs. It should be fast, but actually is quite slow. > > 'dpkg-vendor --query Vendor' takes 40 ms on a recent fast machine > > (Core i5-2400S) with a hot cache and 230 ms on an Intel Atom netbook. > > > > As comparision, the Python version of distro-info took 28 ms, the Haskell > > version 2.5 ms and the final C version only 0.7 ms on the recent fast > > machine. distro-info probably has a similar complexity as dpkg-vendor > > and therefore dpkg-vendor should be faster. > > On my system the following minimal test perl script takes (with a hot > cache) around 6ms: > > ,--- > #!/usr/bin/perl > 1; > `---
This takes 8.5 ms on my Atom netbook. > And the following one in contrast takes around 14ms: > > ,--- > #!/usr/bin/perl > use warnings; > use strict; > 1; > `--- This takes 18.4 ms on my Atom netbook. > The call «dpkg-vendor --query Vendor» takes around 55ms. > > So, while this could certainly be improved in the perl code base, and > patches improving the performance would be appreciated, I'm honestly > failing to see how that's too slow really, or how this is something > that should distract attention from other things. If this script is > being called in a loop or a ton of times during the build process > then something is very wrong somewhere else, and the queried value > should get cached instead or something by the caller. > > Rewritting this in say C, does not seem either really appealing at this > point. Given the above I'm going to be marking this wontfix and closing > if no compelling reasons are given. debchange uses dpkg-vendor to query the vendor. «dch -e ''» takes 1.3 s with the query to dpkg-vendor and 1.1 s without that query. That's 15 % of the total execution time. Having a slow debchange is annoying. The time is accumulating if debchange is run multiple times (like in the test suite of devscripts). dpkg-vendor should be fast to use in it bashrc or in bash completion code. -- Benjamin Drung Debian & Ubuntu Developer
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