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Re: svn commit: r1079008 - /subversion/trunk/subversion/svnadmin/main.c

From: Stefan Sperling <stsp_at_elego.de>
Date: Tue, 8 Mar 2011 15:01:33 +0100

On Tue, Mar 08, 2011 at 01:46:23PM +0000, Philip Martin wrote:
> stefan2_at_apache.org writes:
>
> > Author: stefan2
> > Date: Mon Mar 7 22:57:04 2011
> > New Revision: 1079008
> >
> > URL: http://svn.apache.org/viewvc?rev=1079008&view=rev
> > Log:
> > Set FSFS cache default size to 16 MB. This is the same default as
> > for everybody else, namely the server processes. Thus, it should
> > be reasonable value on the same machines.
>
> 16MB may be "reasonable" for normal usage but it still has a significant
> effect on the testsuite. The testsuite is an unusual access pattern, it
> runs thousands of commands on small repositories. Using a 1MB cache I
> can run the testsuite for ra_local/FSFS in 10m15s, with 16MB cache that
> increases to 12m30s, a 20% increase. There is a similar increase when
> testing ra_svn/FSFS using the default Linux svnserve (a threaded
> svnserve has a shared cache so isn't affected).
>
> svnserve and svnadmin both have a -M option, was there any discussion
> about using a single letter option for this feature? This could be used
> by the testuite to restrict the cache size, but for ra_local/FSFS
> testing there is no way to restrict the svn client.

Shouldn't the cache be off by default?

We have precedence for other features like this that are strictly opt-in,
e.g. memcached support in FSFS. I don't think we should assume that the
new cache code is perfect and enable it by default on any repository for
any 1.7 server. The feature has not had any exposure in the real world yet.

So I think it would be better if the cache was off by default, and must be
enabled in a configuration file. I suppose svnserve and mod_dav_svn
configuration files would be the best location for this, because the
purpose of the cache seems to be to speed up server operation.
An 'svn' process has a short lifetime so the benefit of this cache
seems dubious in that situation. I don't see any reason to even provide
a way to turn it on there.
Received on 2011-03-08 15:02:10 CET

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