performance

When facing problems regarding memory consumption of a Java application, the JDK contains a number of useful tools to help you understand what is going on. You can get a list of the tools on this page.
One of these tools is "jmap". Jmap will let you now (among other things) know what objects are using your precious memory.

Cool!
...
except that when you try to use jmap on Ubuntu 11.04 with a Sun JVM 6, you will get this error message:

Attaching to process ID 12450, please wait...

I used to profile my Java applications with the TPTP Eclipse plugin. It was admittedly a nightmare to install, but once you had it running, it was a fairly efficient tool. Alas, to my dismay, I realized that TPTP is no more. The project was dropped from the latest Eclipse release train (Indigo). And of course, one week after the new Eclipse release, I have a need to profile a remote server.

We have been running a Red5 server for quite some time, and as our application was getting more popular, we happened to see new errors we had never seen before. Actually, we saw a bunch of "Too many open files" exceptions in the logs, and most users could not connect anymore to our application.

Dans cet article, je vais expliquer comment installer APC sur Ubuntu 10.04.
APC est un cache d'opcode (même un peu plus que ça). Quand un script PHP est exécuté, il est d'abord compilé en interne par PHP. PHP ne stocke pas le résultat compilé du script et donc, à la prochaine exécution du script, PHP le recompilera. APC est conçu pour stocker le résultat compilé dans son cache. Ainsi, losque PHP exécute le script, APC lui servira directement le script compilé. PHP n'aura pas besoin de recompiler le script et économisera donc beaucoup de temps.