On Fri, Mar 18, 2022 at 8:27 AM Marc Serra <mserra@xxxxxxxxx> wrote:
>
> Thank's for your comments Frank,
>
> Reading the Apache documentation
> (https://httpd.apache.org/docs/2.4/en/mod/mpm_common.html#threadlimit)
> I cannot find the way to calculate an optimal value for ThreadLimit
> and ThreadsPerChild directives for that reason I kept the default
> values (64 and 25).
>
> Can you (or anyone) help me to find the right values?
This script might help for an MPM event configuration based on
MaxRequestWorkers:
```
#!/bin/bash
if [ $# -lt 1 ]; then
echo>&2 "usage: `basename $0` <MaxRequestWorkers>"
exit 1
fi
# Some pre-computations
numWorkers=$1
if [ $numWorkers -lt 1000 ]; then
numProcesses=10
elif [ $numWorkers -lt 10000 ]; then
numProcesses=$(($numWorkers / 100))
else
numProcesses=100
fi
numThreads=$(($numWorkers / $numProcesses))
cat <<EOF
# MPM event settings
StartServers 1
ServerLimit $(($numProcesses * 3))
ThreadLimit $numThreads
ThreadsPerChild $numThreads
MinSpareThreads $numThreads
MaxSpareThreads $(($numWorkers / 2))
MaxRequestWorkers $numWorkers
#ThreadStackSize 524288
MaxConnectionsPerChild 0
EOF
```
For a MaxRequestWorkers of 1500, it gives:
# MPM event settings
StartServers 1
ServerLimit 45
ThreadLimit 100
ThreadsPerChild 100
MinSpareThreads 100
MaxSpareThreads 750
MaxRequestWorkers 1500
#ThreadStackSize 524288
MaxConnectionsPerChild 0
But you didn't describe your workload: static resources, dynamic
content (local with mod_cgid or offloaded with mod_proxy_fcgi),
proxying (HTTP, websocket), etc.
Since your system looks quite capable (RAM/CPU), the limit for
MaxRequestWorkers depends mainly on the average request time (bounded
by timeouts) which you probably should measure for your workload.
Regards;
Yann.
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