[CentOS-devel] mock using yum .repo file?
Jeff Johnson
n3npq at mac.com
Sun Jul 24 21:46:22 UTC 2011
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
> Serbia, Europe
>
> Google is the Mother, Google is the Father, and traceroute is your
> trusty Spiderman...
> StarOS, Mikrotik and CentOS/RHEL/Linux consultant
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