Slow performance on certain pages after upgrade to beta5

[Thomas Kliethermes]

Hi all,
We tried to upgrade our production server to beta5 over the weekend, but 
we noticed much slower response time on the main page.  Previous to 
upgrade, the mainpage came up in less than a second, but with Beta 5 (and 
now Beta 6), it takes 8-12 seconds  (we reverted to xwiki .9).

After moving the database to testing and doing some debugging, I think I 
see part of the problem. The main page shows several news items 
(ArticleClass items), and it appears that they are the cause of the 
slowdown.  If I comment out all the calls to get information about these 
items ( ie $newsdoc.display("title", "view", $newsobject) ) the page 
speeds up significantly (about 1 second per field not retrieved).  If I 
further comment out calls to $xwiki.getLocalUserName, I get another speed 
up of about 2 seconds (there were two calls per news item: for author and 
creator).

The strange thing is, we saw little or no performance difference between 
xwiki .9 and 1 with our test databases, but copy the production database 
to testing and we see it.  If we use xwiki .9, it's fast again.

We had previously added an extensive set of indexes to the mysql database 
to improve performance in .9, but dropping/changing/recreating them had no 
significant effect.

I've tried many debugging steps such as turning on hibernate debug and 
xwiki debug, and can't see any unexpected exceptions on database upgrade., 
and there's nothing unexpected in xwiki.log.

The database is large-ish, 656M, but 601M of that is attachments, and 
deleting the entire contents of xwikiattachments and 
xwikiattachment_content has no effect.  We have 1300 users listed on the 
users page, but I have not tried deleting some yet.

Disabling stats had no impact on performance.

I'm testing on Gentoo Linux, with IBM JDK 1.5, Tomcat 5.5,  and MySQL 5. 

Any ideas about where to start debugging?


-Tom

--
Tom Kliethermes
eSupport Initiatives
IBM Information Management
(913) 599-7240   Fax: (913) 599-8590
http://www.ibm.com/software/data
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