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From Lars Eilebrecht <>
Subject Re: strange usage pattern for child processes
Date Thu, 16 Oct 2008 12:35:18 GMT
Ruediger Pluem wrote:

> This is a pity, because then it will become much harder to debug
> this issue. Any chance you get shell access or that you can instruct
> the administrators in the service company to get the needed information
> for you?

Getting shell access is very unlikely ...
However, initial tests using mod_disk_cache have been very good.
The performance of mod_mem_cache compared to mod_disk_cache is
just very bad ... It seems the main issue is/was that under high
load the child process(es) of Apache just starve while trying to
read something from the mem cache or to write something to it.
But well, without access to the box I couldn't really dig into
what exactly is happening in such a case.

> Ok. MaxSpareThreads is set to 75 with ThreadsPerChild 256. This means
> that StartServers 3 is pointless because after starting *one* process we already
> have way too much spare threads *overall*. So the other 2 processes will get killed
> immediately :-).

Yes you are right, I missed that MaxSpareThreads applies to all child
processes. But I didn't wrote the config. ;-)

However, I still find it a bit odd that we actually use only a single
process and only start using threads of another child process once
all threads of the other process are busy. Wouldn't it make more
sense to keep spare threads in all child processes instead of just
one? Especially if the config has low MaxRequestsPerChild limit.
Or am I missing something?

Lars Eilebrecht

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