Bug#840119: Cannot disable pdiffs

On Sat, Oct 8, 2016 at 2:34 PM, Julian Andres Klode <jak@debian.org> wrote:

On Sat, Oct 08, 2016 at 02:15:27PM +0200, Michael Stapelberg wrote:
> Package: apt
> Version: 1.3
> Severity: normal
>
> Recently (sorry, I don’t know with which version precisely), I have
> noticed that apt acquires pdiffs when running “sudo apt-get update”
> (yes, I have updated my aliases to prefer apt over apt-get for the
> future).
>
> Since pdiffs make updates way slower in my setup, I have pdiffs disabled
> on all my machines using:

Are you running everything from a super hyper fast on-site mirror? Otherwise
I can't believe that statement. PDiffs are tiny, and apply at an incredible
speed, in parallel. And with 1.3, PDiffs are mostly applied while other
indexes are downloading (if any).

I’m on a 1 Gbps fiber connection and can max out that connection to the closest mirrors (e.g. ftp.ch.debian.org, or deb.debian.org via fastly). In this setup, even uncompressing files is usually a slow-down over just downloading the uncompressed version. Applying diffs is usually even slower.

That said, I was under the impression that my observations hold true for slower connections as well, so I’m intrigued.

In any case make sure to time things. Depending on the repository, pdiff
in 1.3 is much faster than before, and the 1.2 pdiff is already much faster
than the 1.1...

What’s a good way to measure this? If there’s no canonical way, I’ll restore /var/lib/apt/lists from yesterday’s backup and use that for benchmarking.

Apart from that, see what Niels said. Site-local settings are best
stored in files starting with 99 IMO.

Thanks, I’ve changed all my files to start with 99.

Best regards,
Michael