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

Sun Jul 24 21:46:22 UTC 2011
Jeff Johnson <n3npq at mac.com>

On Jul 24, 2011, at 5:37 PM, Ljubomir Ljubojevic wrote:

> 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).

I haven't (if you read what I said carefully). Meanwhile mrepo is nicely
done, worth using if you have to babysit tonnes of package metadata. I like
what Dag implements, sane and simple and useful.

> 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.

Please note that I'm speaking way way generally and from memory. What you
gave me was a data point about how well yum performs, and yum is better than
I would have guessed with 10+ repositories underneath it.

Anything else you read is pure crack smoke from me thinking out loud. I
don't even agree with myself often ;-)

73 de Jeff
> -- 
> Ljubomir Ljubojevic
> (Love is in the Air)
> PL Computers
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> StarOS, Mikrotik and CentOS/RHEL/Linux consultant
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