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Re: Directory deltification

From: Stefan Fuhrmann <eqfox_at_web.de>
Date: Mon, 09 Jan 2012 03:21:35 +0100

On 03.01.2012 15:23, Philip Martin wrote:
> Stefan Fuhrmann<stefanfuhrmann_at_alice-dsl.de> writes:
>
>> As of r1224839, FSFS now supports directory deltification.
>> Please review the changes and run tests against different
>> repositories so that we get a better idea of what the costs
>> and benefits are. As soon as I'm back home, I will run tests
>> against the Apache and KDE repositories.
>>
>> So far, I ran tests against the rather small TSVN repository.
>> It seems that we get 50% more capacity / 33% size savings
>> for 0 .. 20% CPU overhead.
> I've been testing this with the old CollabNet Subversion repository, the
> first 40,515 Subversion revisions, on my Linux laptop:
>
> The db/revs directory (unpacked) is 320MB instead of 490MB.
> Loading takes about 12% more CPU.
> Dumping takes about 22% more CPU.
>
> which matches your results. Packing removes about 85MB for both
> repositories.
Thanks for testing!

Packed Apache repo is 29 vs. 41GB.
Packed KDE repo is 39 vs. 69GB.

I also noticed that "svndump dump | svndump load"
is much faster than "svnsync file:// file://". My guess
is that revprop changes are somehow expensive
(even on a RAM disk).
> There are operations where reading the directory representations is more
> dominant. 'svn log' on a path inside the repository uses 100% more CPU.
>
Good finding. I should find some time to look into
this in the next two months or so. My guess is that
combining deltas is the critical operation here.
In that case, almost the whole overhead can be
eliminated.

-- Stefan^2.
Received on 2012-01-09 03:22:11 CET

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