Why does each Apach child process consume 5MB of RAM?

[John Carpenter]

We are running Apache 1.3.33 (PHP 4.3.10, MySQL 4.1) on Debian 3.1 and noticed that each Apache child process takes 5 MB of RAM as soon as it is created (i.e. 5 MB per connection).

Does anybody know what causes it and how we could reduce that to 1 MB or less? Thanks.

[moltar]

What modules do you load in apache?

mod_perl can cause the bloat very easily if you preload many modules.

[John Carpenter]

The following modules are loaded:

mod_php4.c, mod_ssl.c, mod_setenvif.c, mod_expires.c, mod_auth.c, mod_access.c, mod_rewrite.c, mod_alias.c, mod_cgi.c, mod_dir.c, mod_autoindex.c, mod_info.c, mod_status.c, mod_negotiation.c, mod_mime.c, mod_mime_magic.c, mod_log_config.c, mod_chroot.c, mod_macro.c, mod_so.c, http_core.c

[moltar]

Looks ok to me. Another thing to consider is that apache uses shared memory, but the child processes will show the total memory used. What I mean is that it might show 5MB each, but in reality, it may only have 1MB per thread, and 4MB shared between all of them. See how much actual memory is used after you start apache.

[John Carpenter]

Yes, but this probably applies only to Apache 2.x. If I recall correctly, Apache 1.3.x does not support threads. All connections get separate processes, without sharing any memory (unlike in Apache 2.x).

We were actually going to try Apache 2.x (and 2.6.x Linux kernel) but some PHP guys don't recommend it as many php libs aren't thread safe. Anyone knows if MySQL libs are thread-safe today?

Thanks.