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From Hyrum K Wright <hyrum.wri...@wandisco.com>
Subject Re: Directory deltification
Date Tue, 03 Jan 2012 21:39:08 GMT
On Tue, Jan 3, 2012 at 8:23 AM, Philip Martin
<philip.martin@wandisco.com> wrote:
> Stefan Fuhrmann <stefanfuhrmann@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.
>
> There are operations where reading the directory representations is more
> dominant.  'svn log' on a path inside the repository uses 100% more CPU.

Is that peak CPU or overall?  If the I/O overhead went down, I'd
expect the peak CPU usage to go up, but the overall operation time to
drop.

(FWIW, I'm in the midst of loading a copy of the ASF repo using the
new code, and I'll let folks know the results.)

-Hyrum

-- 

uberSVN: Apache Subversion Made Easy
http://www.uberSVN.com/

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