[CentOS-devel] mock using yum .repo file?

Sun Jul 24 21:37:46 UTC 2011
Ljubomir Ljubojevic <office at plnet.rs>

Jeff Johnson wrote:
> On Jul 24, 2011, at 4:35 PM, Ljubomir Ljubojevic wrote:
>> Oh, yeah, yum reads and process xml files, not actual files, so searches 
>> are fast because of it.
> Here's something that might help you:
> Using xml is a significant performance hit: see recent patches to yum/createrepo to
> use sqlite instead of xml … lemme find the check-in claim …
> here is the claim
> 	http://lists.baseurl.org/pipermail/rpm-metadata/2011-July/001353.html
> and quoting
> 	Tested locally on repodata of 9000 pkgs.
> 	Goes from 1.8-> 2GB of  memory in use with the old createrepo code to
> 	325MB of memory in use - same operation - performance-wise it is not
> 	considerably different. More testing will bear that out, though.
> So -- if I believe those numbers -- there's *lots* of room for improvement in yum
> ripping out xml and replacing with a sqlite database. Note that createrepo != yum
> but some of the usage cases are similar. The general problem in yum (and smart and apt)
> is the high cost of the cache load, and the amount of aml that must be parsed/read
> in order to be cached. Adding a sqlite backing store which can just be used, not
> loaded, is a win.

You have mistaken createrepo with yum repomd data. Createrepo is for 
creating actual repository (I use mrepo).

Yum data (repomd, repoview) is different story. Every repository stores 
data in xml file packed with tar. They are unpacked in memory and xml 
data is parsed and put into internal database (and cache). It is very 
much possible that yum internally (for cache) uses sqlite database, 
haven't had the need to research. Using "yum -C <command>" will use yum 
cache rather then download repomd data again.


Ljubomir Ljubojevic
(Love is in the Air)
PL Computers
Serbia, Europe

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