Stas Bekman

I have shown how to measure the size of the process’ shared memory, but we still want to know what the real memory usage is. Obviously this cannot be calculated simply by adding up the memory size of each process because that wouldn’t account for the shared memory. On the other hand we cannot just […]

Now if you need to compare more than variable, doing it by hand can be quite time consuming and error prune. Therefore it’s better to correct the testing script to dump the Perl data-types into files (e.g /tmp/dump.20988, where 20988 is the PID of the process) and then using diff(1) utility to see whether there […]

But as you know in a big community there are always people who love to help, and there is a bunch of developers from all around the world who patch mod_perl, develop entire Perl modules for it, debug the server and advocate it. I’m afraid the list of contributing developers is too long to include […]

So the simplest way is to freeing the parent process is to close all three STD* streams if we don’t need them and untie the Apache socket. In addition you may want to change the process’ current directory to / so the forked process won’t keep the mounted partition busy, if this is to be […]

This code example will allow you to verify that indeed the spawned child process has its own life, and its parent is free as well. Simply issue a request that will run this script, watch that the warnings are started to be written into the /tmp/log file and issue a complete server stop and start. […]

When the process is successfully forked — the parent receives the PID of the newly spawned child as a returned value of the fork() call and the child receives 0. Now the program splits into two. In the above example, the code inside the first block after if will be executed by the parent and […]

The simplest solution is to ignore your dead children. Just add this line before the fork() call: {CHLD} = ‘IGNORE’; When you set the CHLD (SIGCHLD in C) signal handler to ‘IGNORE’, all the processes will be collected by the init process and are therefore prevented from becoming zombies. This doesn’t work everywhere, however. It […]

proper_fork1.pl ————— use strict; use POSIX ‘setsid’; use Apache::SubProcess; my = shift; ->send_http_header(“text/plain”); {CHLD} = ‘IGNORE’; defined (my = fork) or die “Cannot fork: n”; if () { print “Parent 25481 has finished, kid’s PID: n”; } else { ->cleanup_for_exec(); # untie the socket chdir ‘/’ or die “Can’t chdir to /: “; open STDIN, […]

Notice that exec() never returns unless it fails to start the process. Therefore you shouldn’t put any code after exec()–it will be not executed in the case of success. Use system() or back-ticks instead if you want to continue doing other things in the process. But then you probably will want to terminate the process […]

Perl’s system() is not the system(3) call [C-library]. This is how the arguments to system() get interpreted. When there is a single argument to system(), it’ll be checked for for having shell metacharacters first (like *,?), and if there are any–Perl interpreter invokes a real shell program (/bin/sh -c on Unix platforms). If you pass a […]

Now we will use the server to its full capacity, by keeping all MaxClients clients alive all the time and having a big MaxRequestsPerChild, so that no child will be killed during the benchmarking. MinSpareServers 50 MaxSpareServers 50 StartServers 50 MaxClients 50 MaxRequestsPerChild 5000 NR NC RPS comment ———————————————— 100 10 32.05 1000 10 33.14 […]

HW: RS6000, 1Gb RAM SW: AIX 4.1.5 . mod_perl 1.16, apache 1.3.3 Machine running only mysql, httpd docs and mod_perl servers. Machine was _completely_ unloaded during the benchmarking. After each server restart when I changed the server’s configuration, I made sure that the scripts were preloaded by fetching a script at least once for every […]