[ZODB-Dev] Re: ZODB Benchmarks

[Benji York]

Dieter Maurer wrote:
> We do not yet precisely the cause of our commit contentions.

Hard to tell what'll make them better then. ;)

> Almost surely there are several causes that all can lead to contention.
> 
> We already found:
> 
>   *  client side causes (while the client helds to commit lock)
>   
>     - garbage collections (which can block a client in the order of
>       10 to 20 s)

Interesting.  Perhaps someone might enjoy investigating turning off 
garbage collection during commits.

>     - NFS operations (which can take up to 27 s in our setup -- for
>       still unknown reasons)

Not much ZODB can do about that. ;)

>     - invalidation processing, espicially ZEO ClientCache processing

Interesting.  Not knowing much about how invalidations are handled, I'm 
curious where the slow-down is.  Do you have any more detail?

>   *  server side causes
> 
>     - commit lock hold during copy phase of pack
> 
>     - IO trashing during the reachability analysis in pack

The new pack code should help quite a bit with the above (if you're 
saying what I think you're saying).

>     - non deterministic server side IO anomalities
>       (IO suddently takes several times longer than usual -- for still
>       unknown reasons)

Curious.
-- 
Benji York
Senior Software Engineer
Zope Corporation