[ZODB-Dev] Plone/Zeocluster performances problems
Izak Burger
izak at upfrontsystems.co.za
Thu Nov 27 03:41:13 EST 2008
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
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