Description:
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Hi everyone,

I post here a patch that adds the ability to php-fpm to globally limit the global number of php processes.

I made it for personal purpose as I have an "only" 2GB RAM server and several website running on it. 

The problem is the following, when you have several pools :

* Either you choose to have a max_children which is low, you won't go out of memory, but if there is a peak on a specific website while the other ones are quiet, this specific website will be slow, because there will be a queue for the FastCGI requests
* Or you choose to have a max_children which is high and you thus allow peaks on your websites, but if ever there is a peak on several website at the same time, chances are that your server will go out of memory.

With this patch, I introduce a new configuration directive : 

[global]
max_total_processes = 40

40 will be the total number of php processes authorized to be launched in memory at the same time.
When trying to fork a new process (only in the case on pm = dynamic (or pm = ondemand, by the way)) the FPM will look at the current total number of processes that are launched in memory. This is made easy to integrate because FPM already has a fpm_globals.running_children variable referencing the total number of children, all pools summed up. I just had to add a condition, a variable & the ability to read a new config option. SO this is a really, really small patch ! But very useful I think.



The current uploaded patch file has been made for the PHP 5.3 SVN Branch source. Feel free to adapt it to another version of the sources if you want, you will see that it is just a matter of 4-5 changes in the source code.


Hope it will be useful.

-- Troll