Apache2 - Error FD_SETSIZE with fastcgi

Question

I edited __FD_SETSIZE = 1024 to 4096 :

/usr/include/linux/posix_types.h
/usr/include/x86_64-linux-gnu/bits/typesizes.h
#define __FD_SETSIZE        4096

I just compiled my apache2 and libapache2-mod-fastcgi after these changes. How I can be sure I wont get this error :

[Wed Dec 03 10:24:35 2014] [error] [client xx.xx.xx.xx] FastCGI: failed to connect to server "/usr/lib/cgi-bin/php5-fcgi-dev": socket file descriptor (1024) is larger than FD_SETSIZE (1024), you probably need to rebuild Apache with a larger FD_SETSIZE, referer: http://exemple.com/

Is it possible to check this new value to be sure I won't see this error message again ?

Answer 1

Ok so after some tests, it seems I can handle more connection.

After editing these files and recompiling apache2 and libapache2-mod-fastcgi I can now handle more than 1000 virtualhosts with fastcgi without any error 500.