notes/plan for hpss performance work

Andrew Bennetts andrew at
Mon May 5 07:43:56 BST 2008

Martin Pool wrote:
> Andrew and I have been studying hpss performance using -Dhpss and the
> netem hack to simulate a 1000ms rtt network.  Andrew has the full data
> and more details but here are some things we've noticed.

I've dumped the notes and log files I had on my laptop to the wiki:

The notes are rather terse in places, but should be intelligible.  For most of
the cases I've translated the ~/.bzr.log into a more high-level timeline of the
network conversation.  This tends to make repeated/unnecessary operations more
obvious, as well as giving a good overview of where the time is going.

There are some obviously strange things going on, e.g. a push that fails due to
the branches having diverged should fail much faster than it does: it knows the
remote tip revision at 17s, but takes 55s to run because it does odd things like
pushing up a new pack before raising the error. 

People should feel free take a look at the data and tell us about any insights
you have.  Wikis are good for writeups of known facts, but less good for
discussions, so I suggest replying to this thread if you want to dissect some
results.  Feel free to add more relevant experiments to the wiki (but also mail
the list to let people know about them).


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