[ZODB-Dev] Plone/Zeocluster performances problems

[Izak Burger]

Service TICE wrote:
> The server has 8 processors with very low usage but the 12gb RAM are  
> always saturated à 98%. Python process takes 1 to 2gb RAM but there's  
> a lot of "httpd" processes, up to 2.5gb each, their origin remains  
> unknown to us.

Don't be fooled by memory figures. Operating systems always use as much 
ram as possible, whatever isn't used by applications is used by the 
system to cache, buffer, etc to improve performance. Assuming Linux, if 
you run "free" it will report a line for "+- Cache/Buffers" that shows 
RAM that is not used by applications, eg on my desktop machine:

$ free
              total       used     free  shared    buffers     cached
Mem:       1034348    1010988    23360       0      68924     188784
-/+ buffers/cache:     753280   281068
Swap:      2056280     104312  1951968

I have 281MB free :-) Experience has told me not to use more than 80% of 
your RAM for apps, because a bit of buffer and cache is actually needed 
for smooth operation.

The httpd processes are apache child processes. 2.5GB seems a bit too 
much for apache, but even though it seems each one of them occupies 
2.5GB (by running "top" for example), there is a whole lot of sharing 
going on in the shape of shared libraries and the like, so that apache 
doesn't actually use that much per process, but it does use at LEAST 
that much in total, which still seems wrong to me. Try restarting apache 
and see if it persists.

regards,
Izak