On Mon, Mar 22, 2010 at 2:05 PM, Jeff Shell <j...@bottlerocket.net> wrote: > Are there any metrics about how to set the ZODB 'cache-size' (or > cache-size-bytes) option? We've been using '5000' (arbitrarily chosen) for > our Zope 3.4-ish app servers. We have access to zc.z3monitor which can output > the "number of objects in the object caches (combined)" and "number of > non-ghost objects in the object caches (combined)". > > But I don't know understand how to interpret those numbers and use them to > make better settings.
The more interesting numbers are the number of objects loaded per unit time and the number of records added to the cache per unit time, which you can also get from zc.z3monitor. Basically, object loads are somewhat expensive and loads from the ZEO server (and into the cache) are quite a bit more expensive. You want to reduce these numbers by: - Analyzing your application to make sure it isn't loading more objects than it needs to. - Adjusting ZODB and ZEO cache sizes, subject to resource limitations. Some notes: - The Python profiler (cProfile) can help analyze object loading, especially if you have good profiler analysis tools. Unfortunately, I'm not aware of one that's included with Python. My nutty pstats2html script, http://svn.zope.org/Sandbox/J1m/pstats2html.py?view=auto which I wrote before I learned javascript :), can show you who's calling Connection.setstate, and thus, who's doing lots of loads. - Making ZEO persistent cache sizes too large can cause excessive IO on process restart. Jim -- Jim Fulton _______________________________________________ For more information about ZODB, see the ZODB Wiki: http://www.zope.org/Wikis/ZODB/ ZODB-Dev mailing list - ZODB-Dev@zope.org https://mail.zope.org/mailman/listinfo/zodb-dev
