Title: How to optimize Apache for WordPress?
Last modified: August 20, 2016
---
# How to optimize Apache for WordPress?
* [SK](https://wordpress.org/support/users/sooskriszta/)
* (@sooskriszta)
* [13 years, 7 months ago](https://wordpress.org/support/topic/how-to-optimize-apache-for-wordpress/)
* I have recently moved my low-moderate traffic (1000 UAUs, 5000 pageviews on a
busy day) website from shared hosting to a Centos 6 64-bit VPS with Apache and
cPanel running on 4 quad-core processor (likely oversold) and 3GB memory (Xen).
* We’ve had problems from the beginning. The server keeps crashing. It seems PHP
keeps expanding till it consumes all the memory and crashes the server.
* Some folks have suggested that I should abandon Apache/cPanel/PHP/mySQL and go
with nginX/Varnish/PHP-FPM/SQLite. But that’s just not possible for me as I am
not very tech savvy and need a simple GUI like cPanel to be able to manage the
mundane management tasks (can’t afford to hire system administrator or get fully
managed hosting).
* I have come across several posts discussing optimization of Apache for WordPress.
But all of these lead to articles that are pretty dated such as this ~4 year
old one from Jan 2009 – [http://thethemefoundry.com/blog/optimize-apache-wordpress/](http://thethemefoundry.com/blog/optimize-apache-wordpress/)
* The article is pretty detailed and seems helpful, but I stumble even on the first
step. httpd.conf only has 2 loadmodule commands
LoadModule fastinclude_module
modules/mod_fastinclude.so LoadModule bwlimited_module modules/mod_bwlimited.
so
* So I go total bust right there. Further, httpd.conf says
Direct modifications
to the Apache configuration file may be lost upon subsequent regeneration of
the configuration file. To have modifications retained, all modifications must
be checked into the configuration system by running: /usr/local/cpanel/bin/apache_conf_distiller
I am having trouble finding where to change the modules in WHM.
* Please can someone help me with updated guidelines on how to optimize Apache
for WordPress? Many thanks!
* P.S. The WordPress installation also has WP Super Cache installed.
Viewing 3 replies - 1 through 3 (of 3 total)
* [s_ha_dum](https://wordpress.org/support/users/apljdi/)
* (@apljdi)
* [13 years, 7 months ago](https://wordpress.org/support/topic/how-to-optimize-apache-for-wordpress/#post-3150656)
* > Some folks have suggested that I should abandon Apache/cPanel/PHP/mySQL and
> go with nginX/Varnish/PHP-FPM/SQLite
* No idea how you’d go with SQLite. That is a completely different database than
what WordPress uses. I am considering nginX though. Anyway, you are correct,
that kind of conversion may not be the thing to try for someone new to server
management.
* Apache2 can run in two ‘modes’– prefork and worker. The latter is a second generation
threaded service. The former spawns individual processes. The latter is better
in theory but there are a lot of cautions when it comes to using it in combinations
with PHP.
* If you open, ” /etc/httpd/conf/httpd.conf”, you should see:
* ```
StartServers 8
MinSpareServers 5
MaxSpareServers 20
ServerLimit 256
MaxClients 256
MaxRequestsPerChild 4000
```
* ```
StartServers 4
MaxClients 300
MinSpareThreads 25
MaxSpareThreads 75
ThreadsPerChild 25
MaxRequestsPerChild 0
```
* That is the default configuration for Apache2 on Centos 6 as far as I am aware.
At least that is what it looked like when I got to it. It also appears to default
to ‘prefork’. The problem is with the ServerLimit and MaxClients lines. Every
time a client is spawned it grabs memory. Now, with 256 clients and 3GB RAM,
each client can only use about 12MB, and that isn’t allowing any memory for MySQL
or the rest of the system. WordPress defaults to 32MB (64MB for multisite) max
memory. Meaning that chances are with enough traffic there comes a point when
Apache tries to spawn a process and there is no memory to use. The server will
try to use swap space if it can and you end up with situation where RAM gets
written to swap space and back again over and over and the system chokes on its
onw efforts to manage memory and more or less fails. There is a geek cool name
for it but I can’t remember– oh the shame!
* So, you need to cut the numbers of clients to the point that you won’t be exhausting
memory. You will need to figure out how much the system – Apache uses. Let’s
assume 500MB. You have 2500MB available. At 32MB max memory, you should be able
to spawn 78 processes without running out of RAM. Or…
* ```
StartServers 8
MinSpareServers 5
MaxSpareServers 20
ServerLimit 78
MaxClients 78
MaxRequestsPerChild 4000
```
* That MaxRequestsPerChild number is how many times the process will be reused
before it is closed and a new one started. Reusing is faster but the process
doesn’t release memory until it is closed.
* StartServers is the number of processes that are created when Apache starts,
whether you need them or not and MinSpareServers is the number of open processes
kept in the wings just in case.
* As you may have guessed, I have some familiarity with this. I also run WordPress
on a 64bit Centos 6 VPS. I am still working on the solution and this is what
I have so far. I can’t promise anything at this point and, please, if anyone
can correct me on something do so.
* Thread Starter [SK](https://wordpress.org/support/users/sooskriszta/)
* (@sooskriszta)
* [13 years, 7 months ago](https://wordpress.org/support/topic/how-to-optimize-apache-for-wordpress/#post-3150679)
* Thank you so very much for the descriptive and easy-to-understand response.
* My current httpd.conf has the following settings related to what you wrote above
* ```
Timeout 300
TraceEnable On
ServerSignature Off
ServerTokens Full
FileETag None
StartServers 5
MinSpareServers 5
MaxSpareServers 10
ServerLimit 256
MaxClients 150
MaxRequestsPerChild 10000
KeepAlive On
KeepAliveTimeout 6
MaxKeepAliveRequests 75
```
* So I will have to try reducing
MaxClients and MaxRequestsPerChild settings.
* Could you please also explain in layman terms (or point me to a resource) the
meaning/purpose of
* > ServerLimit
> MaxClients MaxRequestsPerChild
* Specifically, what are servers, clients and children in this context? What does
process mean?
* My wp-config says
* > define (‘WP_MEMORY_LIMIT’, ‘2048M’);
* Should I also reduce the wp_memory_limit?
* [s_ha_dum](https://wordpress.org/support/users/apljdi/)
* (@apljdi)
* [13 years, 7 months ago](https://wordpress.org/support/topic/how-to-optimize-apache-for-wordpress/#post-3150682)
* Again, still working through the details myself but…
1. ServerLimit: The maximum number of processes that will be created over the life
of the server. For prefork, this is basically the maximum possible value for
MaxClients.
2. MaxClients: The maximum possible simultaneous connections. Think of it like
cloning. If your Apache server is busy it will make a new copy of itself to
help handle the traffic, but will only create copies up ServerLimit. For prefork,
this and ServerLimit should be the same or very close with MaxClients never
exceeding ServerLimit.
3. MaxRequestsPerChild: The number of requests a process will handle before being
killed, and another one created. Reusing is faster but memory gets ‘locked’
up. Say you have a script that normally uses 5MB memory. Each process will use
only 5MB. If, however, one rare function uses 80MB, that process (child) will
hang onto 80MB until it gets killed, which is a big waste of memory. So what
you want is a number low enough to moderate that memory consumption but high
enough that you aren’t spawning processes all the time, which is ineffecient.
* Here is the Apache Docs for these settings: [http://httpd.apache.org/docs/2.2/mod/mpm_common.html](http://httpd.apache.org/docs/2.2/mod/mpm_common.html)
* [A process is a program that is in the process of executing.](http://linuxgazette.net/133/saha.html)
It is a running program.
* Yes, 2048MB is much too high. If you need that much you have very serious structural
problems with the website. Stock WordPress runs fine with 32MB. Right now, my
processes are using 55MB but that is an extensively modified system that does
a lot of work– far above and beyond what WordPress would normally need (but still
below what multisite requires).
Viewing 3 replies - 1 through 3 (of 3 total)
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## Tags
* [apache](https://wordpress.org/support/topic-tag/apache/)
* [Crash](https://wordpress.org/support/topic-tag/crash/)
* [server](https://wordpress.org/support/topic-tag/server/)
* [vps](https://wordpress.org/support/topic-tag/vps/)
* In: [Fixing WordPress](https://wordpress.org/support/forum/how-to-and-troubleshooting/)
* 3 replies
* 2 participants
* Last reply from: [s_ha_dum](https://wordpress.org/support/users/apljdi/)
* Last activity: [13 years, 7 months ago](https://wordpress.org/support/topic/how-to-optimize-apache-for-wordpress/#post-3150682)
* Status: not resolved
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