Zsync for Packages files

[Max Bowsher]

Lars Wirzenius wrote:
> ma, 2009-07-20 kello 22:46 +0200, Tollef Fog Heen kirjoitti:
>> ]] Max Bowsher 
>>
>> | That's interesting - I would have thought that it would simply lead to
>> | many small pdiff files being created, but the system overall still
>> | working fine. How is the usability damaged?
>>
>> You'll need to get quite a lot of small files, which means you get hit
>> by TCP's slow start algorithm again and again rather than just grabbing
>> one big file once.
> 
> Surely apt uses a single TCP connection to fetch all the pdiff files?
> That is, HTTP pipelining, or whatever it is called, to do several HTTP
> requests over a singel TCP connection.

Based on a quick look at a Wireshark trace (admittedly not downloading
pdiffs), APT does both keepalive and pipelining. Therefore TCP slow
start is not an issue.

> At this point we're in speculation territory. Does someone have the
> ability to do a quick benchmark to see how much data a week's worth of
> Packages file updates for karmic takes, using pdiffs? I'd be happy to
> provide the files I snapshotted for this, but I don't have the time to
> actually do the benchmark.

I might be able to have a go at this.

Does anyone know where Debian's pdiff generation code lives? Somewhere
in dak, I guess?

Max.

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