[imp] Horde/IMP performance problems

[lst_hoe02 at kwsoft.de]

Zitat von Jochen Roderburg <Roderburg at Uni-Koeln.DE>:

> Hello Andreas,
>
> Thanks for many more hints about the possible problems.
>
> Only one remark at the moment about one of the points:
>
>>> And database traffic in general: During my unintended "public   
>>> performance test" I had a situation where database connection were  
>>>  not all accepted by our MySQL server and I saw many  
>>> warnings/errors  in the imp log with the names of the new  
>>> groupware components which  we had not in use before. I got the  
>>> impression that these program  parts create a lot of background  
>>> activity even when they are not  really used.
>>
>> You have not really mentioned in your first post but from this i  
>> guess  the biggest problem is the DB load?
>
>> - You need to allow as many connections to the database as you have  
>>  webserver processes and maybe persistant connections could help.
>>
>
> This last one was the simple cause of the DB connection problems. I  
> had increased the MaxClients on the Apache side to a higher values  
> than the max_user_connections on the DB server.

This for sure lead to trouble...

> OTOH there was no significant load on the DB server, only on the webserver.
> I have yet to determine the real bottleneck, enough memory was  
> available, CPU was more saturated. What several people noted, that  
> there was a unusual high amount of system CPU used, but so far no  
> one had a good idea where this could come from.

It may be caused by many httpd daemons fighting to get a database  
connection. Other reasons could include high I/O load (what was the  
IO-wait percentage) or process scheduling but the last one should only  
be noticeable at very high process counts.
It is uncommon for sure because CPU sys load means the kernel is  
working hard while for Horde/IMP the most processing should be in  
user-space.

Regards

Andreas


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