Re: Is ServerLimit 256 in prefork mode somehow hardcoded?

[Marc Serra <mserra@xxxxxxxxx>]

https://httpd.apache.org/docs/2.4/en/mod/mpm_common.html#serverlimit

There is a hard limit of ServerLimit 20000 compiled into the server (for the prefork MPM 200000). This is intended to avoid nasty effects caused by typos. To increase it even further past this limit, you will need to modify the value of MAX_SERVER_LIMIT in the mpm source file and rebuild the server.

Missatge de Alois Treindl <alois@xxxxxxxx> del dia dt., 1 de juny 2021 a les 11:02:

I am using Apache on RHEL 7 since along time.
httpd-2.4.6-97.el7_9.x86_64

I use it with mod_mpm_prefork module, the default on Redhat.

I see, shortly after startup, messages in errorlog like
AH00161: server reached MaxRequestWorkers setting, consider raising the MaxRequestWorkers setting

I have tried to do that
<IfModule mpm_prefork_module>
    StartServers          20
    MinSpareServers       10
    MaxSpareServers       20
    ServerLimit           512
    MaxRequestWorkers     512
    MaxConnectionsPerChild  10000
</IfModule>

I also tried much higher values of ServerLimit and MaxRequestWorkers, like 6400 or 30'000

It makes no difference, the error message appears.

In server-status, I always see four lines of 64 servers, i.e. a total of 256 servers shown, like this:

.R_RRRRR_RRRRRKCCC_C..R_RRRKRRCC.R_CCKRKRRRRRKC.KRKR_R.__RKCRRRK
.KKRWRC_R_RCRRCKR_KRKKRRKKKKRKRC.C_RRRKR_RRRRC.K................
................................................................
................................................................

How can I get beyond these 256 servers?

The machine has 64 cores, and 132 Gb RAM.

I know that I can switch to mod_mpm_event, but before I go that way, I would like to know why I cannot more than 256 servers in prefork mode.

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