Software Management call for RFEs

Jan Zelený jzeleny at redhat.com
Mon May 27 08:24:33 UTC 2013


On 27. 5. 2013 at 09:43:15, Florian Weimer wrote:
> On 05/27/2013 09:32 AM, Jan Zelený wrote:
> > On 25. 5. 2013 at 09:34:32, Nico Kadel-Garcia wrote:
> >> On Wed, May 22, 2013 at 11:55 AM, Michael Ekstrand <michael at elehack.net>
> > 
> > wrote:
> >>> Performance improvement: improve scaling to 5K+ installed packages.
> >> 
> >> * Amen. This is particularly compounded by poor caching default
> >> behavior, so that a few yum commands in a row each wind up reaching
> >> out to downloading metadata again, and again, and again.
> >> 
> >> I think this can be addressed by moving the metadata updates to a
> >> different function, and calling it *separately* only as needed. The
> >> Debian "apt" tool does this quite effectively.
> > 
> > Unfortunately there is not much we can do about this. Debian has
> > completely
> > different repository policy - they keep all versions of packages in the
> > repo so there is no need to update metadata on client machines every
> > time.
> I don't quite understand this comment.
> 
> Debian repository policy varies quite a bit.  Some repositories keep old
> versions, some don't.  Mostly the latter, actually, because not all
> repository managers (there a couple of implementations) can deal with
> multiple versions for a single package/architecture combination.

I'm sorry but the Debian repositories say otherwise, see Iceweasel for 
instance:

http://ftp.cz.debian.org/debian/pool/main/i/iceweasel/

Multiple old versions are kept in there. That's why they don't need to update 
their metadata every single time - the old ones are simply still valid.

> As far as I can tell, the main difference is that apt-get and apt-cache
> read very few, relatively large files at the beginning, so they don't
> block on disk reads early.
> 
> dpkg, on the other hand, uses a database scatter across many small files
> on disk, so you get the delay only when you actually install or remove
> any packages.  At the beginning, this is quite fast, but eventually, the
> files will be scattered quite badly, and there is a considerable delay
> at this step.

This part is about disk read-write but that was not what I was writing about. 
>From my experience users mostly complain about the metadata download which is 
explained above.

Thanks
Jan


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