Bug#810898: apt: "apt-get update" (1.2) very slow with compressed indices and debtags
Control: severity -1 normal
Control: reassign -1 debtags
On Wed, Jan 13, 2016 at 03:00:48PM +0100, Vincent Danjean wrote:
> Package: apt
> Version: 1.2~exp1
> Severity: important
>
> Hi,
>
> New apt from experimental with compressed indices and debtag installed
> makes "apt-get update" very slow. I downgraded apt to be sure the problems come from the
> new version (perhaps the problem comes from the compressed indices, I never try them with
> the previous apt version)
That's the point. In old versions it would be even worse. And most clients
do not support them at all.
> I report this bug to apt as it is triggered by this new version.
> However, the fix would possibly to be write in debtag itself (but, in
> this case, apt should add a Breaks: debtags (<<fixed-version) )
It probably would have the same issue if you use acquire::GzipIndexes
with older versions, or even worse, as gzip is far slower than lz4.
So it's not really a new bug, and a Breaks would be too exterme,
so I reassign this to debtags. I assume that debtags is not reading
the lists in sequence, but rather jumps around in them, which is
extremely costly with any compressor.
If it goes through the cache and then looks up each packages in the
Packages files, the issue can be countered by sorting the list of
packages by name, as that ensures mostly-linear reads.
--
Julian Andres Klode - Debian Developer, Ubuntu Member
See http://wiki.debian.org/JulianAndresKlode and http://jak-linux.org/.
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