On Tue, Feb 18, 2014 at 8:59 PM, Dylan Jay <d...@pretaweb.com> wrote: > Hi, > > I'm seeing a a ZCatalog reindex of a large number of objects take a long time > while only using 10% cpu. I'm not sure yet if this is due to the size of the > objects and therefore the network is saturated, or the ZEO file reads aren't > fast enough.
How heavily loaded is your storage server, especially %CPU of the server process? Also, are the ZODB object or client caches big enough for the job? > However looking at the protocol I didn't see a way for code such as the > ZCatalog to give a hint to ZEO as to what they wanted to load next so the > time is taken by network delays rather than either ZEO or app. Is that the > case? It is the case that a ZEO client does one read at a time and that there's no easy way to pre-load objects. > I'm guessing if it is, it's a fundamental design problem that can't be fixed > :( I don't think there's a *fundamental* problem. There are three issues. The hardest to solve isn't at the storage level. I'll mention the 2 easiest problems first: 1. The ZEO client implementation only allows one outstanding request at a time, even on a client with multiple threads. This is merely a clumsy implementation. The protocol easily allows for multiple outstanding reads! 2. The storage API doesn't provide a way to read multiple objects at once, or to otherwise hint that additional objects will be loaded. Both of these are fairly straightforward to fix. It's just a matter of time. :) 3. You have to be able to predict what data are going to be needed. This IMO is rather hard, at least at a general level. It's what's left me somewhat under-motivated to address the first 2 problems. We really should address problems 1 and 2 to make it possible for people to experiment with approaches to problem 3. Jim -- Jim Fulton http://www.linkedin.com/in/jimfulton _______________________________________________ For more information about ZODB, see http://zodb.org/ ZODB-Dev mailing list - ZODB-Dev@zope.org https://mail.zope.org/mailman/listinfo/zodb-dev