Forum OpenACS Q&A: Re: Kernel Parameter: PerformanceModeP and PermissionCache

3: Re: Kernel Parameter: PerformanceModeP and PermissionCache (response to 1)

Posted by Nima Mazloumi on 04/14/05 06:45 PM

We had a case today where 800 - 1000 students tried to register for a course. The peak was around 250-260 concurrent users and the server got so slow that would had to wait for 1-3 minutes for each link to render. So we are lookinf for solutions to improve performance.

here the ideas:
- seperate database from aolserver?
- load-balancing by using several aolservers and one database?
- tune postgres (but we I have no idea which settings have to be taken)
- set some parameters in oacs kernel?
- ???

6: Re: Re: Kernel Parameter: PerformanceModeP and PermissionCache (response to 3)

Posted by Patrick Giagnocavo on 04/14/05 07:32 PM

In some respects, you are asking the wrong question. The first question to ask is, what is the resource that is being used most heavily? Is it disk I/O, CPU usage, network bandwidth, or RAM/virtual memory? My guess is disk I/O or RAM.

Once you know what the bottleneck is, then you can figure out how to solve it.

Use iostat, sar, and vmstat to figure out what is going on. I have found sar to be useful, but you have to turn it on first and it is more of a "what happened" rather than "what is currently happening" tool.