In general, PHP does a realpath() on files (most importantly included files) so that when include_once() and other PHP functionality needs to know if two file paths are identical it will give a definite answer. realpath() itself is quite a slow function (especially on some specific OS) and therefore should be saved when possible.
As it is rare that a realpath() for a certain file path + cwd combination ever changes, it's a perfect candidate for caching (actually a realpath() can only really change if you are adding/changing symlinks).
Therefore, this patch implements caching of realpath() calls. There are two INI settings which can be changed:
realpath_cache_size - Size of cache (default's to 16K; if set to 0 it turns of caching).
realpath_cache_ttl - Time to live for cache entry (default 120 seconds; if set to 0 then doesn't refresh).
On a loaded side even a small TTL should do the trick, although it might make sense to raise the TTL to something much higher than 120 seconds because as I said, it doesn't usually change.
Hope that's enough info.
Andi
At 07:24 PM 9/20/2004 -0700, Andi Gutmans wrote:
Thanks for pointing out that the attachment didn't make it through. You can find it at:
http://snaps.php.net/~andi/realpath_cache2.diff
Andi
At 06:28 PM 9/20/2004 -0700, Andi Gutmans wrote:Hi,
Attached is the promised patch to do realpath() caching.
You can set cache size and TTL via the php.ini (default is 2 minutes TTL and 16K memory).
It doesn't use the SAPI time() but uses the syscall time() because it seemed to be slightly faster but we can adjust it to use the SAPI one if anyone measures a difference in performance (might depend on the OS).
Feedback welcome.
Also any feedback on the VM patch? I'd like to commit it soon but I haven't heard anything from this list (people were saying they wanted to review it).
Thanks, Andi
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