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Re: Impact of window size on delta performance

From: Karl Fogel <kfogel_at_galois.collab.net>
Date: 2000-10-13 04:25:31 CEST

Greg Hudson <ghudson@MIT.EDU> writes:
> It does, of course, at the front of each window of data. Source view
> offset, source view length, target view size.

Apologies. I read notes/svndiff, but should have looked at the code.

> There's no compelling reason to use a smaller window for a smaller
> file if you have the memory to spare. I know I said "the optimal
> window size depends on the input data," but what I really meant is
> "the sweet spot for delta size performance depends on." You'll always
> do okay using larger windows than is necessary to reach the sweet
> spot.

I see.

> The real question is what is a reasonable amount of memory for
> subversion programs to use. That depends more on the machine the
> subversion code is running on (and the machine the code is talking to,
> when you're transmitting diffs across the wire) than the input data.
> I think 100K windows is enough to handle quite a bit of data movement
> while still being relatively innocuous on most machines.

Definitely agree with the increase in window size... and even think
you could bump it further. Optimizing for network performance is a
pretty high priority, and I don't think 100k is really pushing
anyone's memory resources (especially given that the client is rarely
handling more than one or two windows at a time, and we can probably
assume that the busier a server is, the more memory it will have
anyway).
Received on Sat Oct 21 14:36:11 2006

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