[Zope] RE: Performance issues - excessive object loads

[Gerry Kirk]

Hi again,

I'm getting reports right now that the system is slow. There are a few
people doing a lot of editing at the moment. Looking at the activity
log, I see in the past hour:

Object stores: 12,500
Object loads: 9267
Connections: 679

# objects in db: 182K
# objects in mem from all caches: 29K
Max # objects per cache: 15K

Cache Name	Number of objects in memory 	Number of ghost objects
1		10525					55742
2		3669					12546
3		4589					15934
4		10239					61065
Total		29022

You mentioned it might be better to have two threads with larger caches
instead of 4. How do I determine which way to go?

I haven't seen any flipping cache messages since June 14 now. Is it
possible to have too large a zeo client cache file?

Thanks,
Gerry
	
> -----Original Message-----
> From: Casey Duncan [mailto:casey at zope.com] 
> Sent: June 8, 2004 10:23 AM
> To: Gerry Kirk
> Cc: zope at zope.org
> Subject: Re: Performance issues - excessive object loads
> 
> 
> On Tue, 8 Jun 2004 10:04:05 -0400
> "Gerry Kirk" <gerry at dioceseonline.com> wrote:
> 
> > > Generally increasing the cache size is the most effective way to 
> > > reduce loads. Try increasing the cache to say 15000 (assuming you 
> > > have enough RAM on the server) and see how that affects the load 
> > > rate. 2000 is a relatively low setting, but that really 
> depends on 
> > > the size of the ZODB. How many objects are in your ZODB? Are you 
> > > using ZEO? (I assume not)
> > >
> > showing 176000 objects
> 
> A cache size of 2000 only allows 1% of the objects to be 
> cached at once. 15000 is much better (about 8.5%), but you 
> could still go higher if you have the RAM.
> 
> Since the cache is per-thread, it can sometimes be better to 
> run fewer threads with bigger caches. You could try lowering 
> the number of threads to 2 and doubling the cache size. This 
> may be better than 4 at 15000, but it depends heavily on your 
> application and the load it experiences
>  
> > I am using ZEO with one ZEO client, running on same server.
> > 
> > I'll try using 15,000 cache setting. This is what I now have in my
> > zope.conf:
> > 
> >  <zodb_db main>
> >    cache-size 15000
> >    <zeoclient>
> >      cache-size 20000000
> 
> Try upping the client disk cache size as well. This looks 
> like the default (20MB) which is quite small. I would 
> probably multiply this by 10-30x. An indication for a too 
> small ZEO client cache is many "Cache flip" log messages from Zope.
> 
> -Casey
>