On Fri, 2008-11-21 at 07:31 +0100, Andreas Jung wrote: > Hi there, > > we are currently doing consultancy work for a bigger Zope-based CMS > project (lotes of users, lots of concurrent editors/write). Plone and > CMF are basically what we are looking into right now. It is well-known > that Plone is poor on concurrent write. It is basically impossible > creating more than 3-4 objects per second on decent hardware. On > observation we made was that Plone causes transaction size of 30k-100k > per each new object (this is also true trivial changes on existing > content objects). So I thought this might be a limiting factor and > looked at CMF. The transaction sizes under CMF are much smaller - > typically between 2k and 4k for new objects or object changes which is > looking good at the first glance. However the transaction size does not > seem to have any impact on the number of simulataneous writes. > I wrote script simple script like this: > > results_folder[randint(1,500)].invokeFactory(Document, some_id) > > where result_folder is a btree based folder containing 500 other empty > btree folders. > > Running 'ab2 -n 100' against the site would create 100 new documents > distributed over the subfolder (avoid conflicts errors here). > The performance was nearly as bad as with Plone. It was hard getting > more 4-6 new objects per second out of a standard CMF site (2.1, > zope.schema-based types). Even variations of the zserver-threads and the > ab2 concurrency level did not help much. > > hmm....so why is CMF here nearly as bad a Plone. In Plone we know that > everything is indexed various times (also in CMF I think) but Plone has > much more indexes and metadata compared to CMF. A request in Plone goes > through much more layers than in CMF....I am currently clueless > interpreting the results. My current interpretation is: a custom > CMF-based implementation of a CMS will be comparable slow/fast as an > out-of-the-box solution?!
I also suspected transaction size a while back but found that it doesn't really impact on write performance. The one thing that stood out clearly was the time it takes to index objects. I managed writes of up to 20 objects per second if I created the object with _setObject while suppressing all events and manually re-indexing the object after creation. Indexing in Plone improved once we cached the expensive Schema lookup that is made for each attribute (see discussion on this in plone-dev) but this shouldn't be an issue in CMF. Maybe there is something else in CMF that slows down attribute access when objects are indexed. I can almost guarantee that there is some application code that slows down writes, since I know now that indexing and object creation is relatively fast. -- Roché Compaan Upfront Systems http://www.upfrontsystems.co.za _______________________________________________ Zope-CMF maillist - Zope-CMF@lists.zope.org http://mail.zope.org/mailman/listinfo/zope-cmf See https://bugs.launchpad.net/zope-cmf/ for bug reports and feature requests
