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Re: svn commit: r1637184 - in /subversion/trunk/subversion: libsvn_fs_fs/ tests/libsvn_fs/

From: Branko Čibej <brane_at_wandisco.com>
Date: Tue, 11 Nov 2014 23:10:06 +0100

On 11.11.2014 20:40, Evgeny Kotkov wrote:
> Branko Čibej <brane_at_wandisco.com> writes:
>
>>> From the performance point of view there will be no big benefits to enable
>>> log addressing for an existing repository, because the existing old part
>>> of the repository will remain to be addressed physically.
>> I disagree with your assessment. Certainly, as long as there are "live"
>> delta chains in the repository that reach all the way into
>> physically-indexed content, there will less performance benefit from
>> logical addressing than in a "pure" FSFSv7. But this state will not
>> persist "forever", certainly not for actively changed content.
> I did a small attempt in measuring the performance benefits of the mixed-mode
> addressing. Please note that these results are only provided for the Windows
> platform and only cover basic operations over two protocols. My tests were
> done under Windows 8.1 Professional (Apache HTTP Server 2.2.29, serf 1.3.8),
> a part of the batch file covering the 'file://' protocol is attached.

[...]

> - The repository received an upgrade to FSFS7 with mixed-mode addressing and
> has been accumulating new logically addressed revisions for one year. A
> corresponding revision span is the following:
>
> (r24752, 9/10/2013 → r25851, 9/10/2014)
>
> - The repository received an upgrade to FSFS7 with mixed-mode addressing and
> has been accumulating new logically addressed revisions for three years. A
> corresponding revision span is the following:
>
> (r21959, 9/10/2011 → r25851, 9/10/2014)

[...]

> I do not want to make any conclusions on this topic. However, my results do
> not show any obvious advantage of having the mixed-mode addressing enabled for
> the sample (http://tortoisesvn.googlecode.com/svn/) repository. Even after
> *three* years of logically addressed revisions landing into the repository,
> the performance gains still fluctuate around zero.

Thanks for taking the time to measure this. The results are interesting.

I'll just point out that saying "one year" and "three years" is
misleading; we're actually looking at approximately 1000 and 4000
revisions, which in the default configuration is 1 and 4 packfiles.
That's not a lot, really.

On the other hand, any benefits from reordering and logical addressing
in a mixed-addressing repository would be spread across individual files
and directories; that is, the benefits would really start showing up
once /most/ files and dirs have had more than the delta-chain limit
number of new revisions.

So yeah ... most repositories probably aren't busy enough for this to
make a visible impact (I know the ASF repo isn't; it gets a lot more
commits in a year, but these are fragmented amongst 150+ projects and
their branches). I concede that, in the light of this, supporting
mixed-mode addressing is not that important.

-- Brane
Received on 2014-11-11 23:12:09 CET

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