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I recently moved my mpm from perfork to event (& also mod_php (php7.0) to php-fpm (proxy_fgi)) I estimated my max concurrent connection load to be around 300. So i set the following configuration in mpm_event.conf

StartServers                     5
MinSpareThreads          25
MaxSpareThreads          75
ThreadLimit                      64
ThreadsPerChild          35
MaxRequestWorkers         350
MaxConnectionsPerChild   0

Now I see some strange behavior when I observe the apache2 process and total threadcount using ps

Normally I have around 12-13 total apache2 processes (ps aux | grep apache2 | wc -l). Considering one to be parent.. so it is about 10-11 children. Further if I see the total threads count from apache2 with

ps -o nlwp $(pidof apache2) | tail -n +2 | awk '{ num_threads += $1 } END { print num_threads }'

I observe 408 threads for a long time.. So my questions are:

  • how is it possible that total # of threads increasing beyond MaxRequestWorkers (350)
  • how is it possible that total # of child processes increase beyond StartServers (5)
  • What is the justification for 408? (12*34?) and is my traffic hitting a limit?

Thanks for your help in advance

dgarg
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1 Answers1

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I am observing similar behaviour. With default MaxRequestWorkers 150, I reach up to 301 threads - i.e. 1 parent and 2* MaxRequestWorkers threads.

I tested this by setting MaxRequestWorkers as 40 and I reached 81.

Can anyone confirm this Apache behavior?

P.S. I am running Apache2 as prefork, i.e. ThreadLimit and ThreadsPerChild are not used IMHO.

dferbas
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  • This does not really answer the question. If you have a different question, you can ask it by clicking [Ask Question](https://serverfault.com/questions/ask). To get notified when this question gets new answers, you can [follow this question](https://meta.stackexchange.com/q/345661). Once you have enough [reputation](https://serverfault.com/help/whats-reputation), you can also [add a bounty](https://serverfault.com/help/privileges/set-bounties) to draw more attention to this question. - [From Review](/review/late-answers/512409) – Dave M Feb 16 '22 at 22:16
  • What I am saying is - I have a suspection number of threads reach 2* MaxRequestWorkers + 1 (parent thread). Every client request forks another thread probably because of using php. As I am using Apache in prefork mode, I can't be sure the same is also true for the event MPM. – dferbas Feb 18 '22 at 10:35