Simetrical wrote:
On Mon, Jul 7, 2008 at 8:55 AM,
<demon(a)svn.wikimedia.org> wrote:
Log Message:
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Cache the SVN version so we're not doing a filesystem read every time Special:Version
(or APIQuerySiteInfo) asks for it.
This appears to mean that the version will be inaccurate for up to an
hour after svn upping. This is a regression which could be
potentially significant; it's fairly important to know the exact
revision if an error is spotted right after an svn up. Is there any
reason to think that the benefit is worth it? Operating systems do
have disk caches, which are a lot faster than a memcached call if they
get hit, and we're only talking about a vanishingly small minority of
page views here anyway. I would suggest this be backed out unless
this is causing a demonstrable performance problem.
We do a fair few filesystem reads on each request in the Wikimedia
cluster, served from kernel cache, they're quite a bit faster than
memcached. Obviously if you have your script directory on NFS, it's going
to be slow, but still comparable to memcached. Maybe if the NFS server was
overloaded or underpowered, then there would be an argument for it.
-- Tim Starling