[dokuwiki] Sleeping vs. trolling
- From: "Joe Lapp" <joe.lapp@xxxxxxxxx>
- To: dokuwiki@xxxxxxxxxxxxx
- Date: Wed, 17 May 2006 11:05:33 -0500 (CDT)
I was looking at Dokuwiki's file locking mechanism and noticed that it trolls
rather than sleeps. I was expecting a call to usleep() for a random number of
microsecs so that the thread isn't hogging clock cycles and reducing overall
server performance. (It would be random to help de-sync and spread out
multiple simultaneous attempts to access the already-locked file.)
Is there a reason why io_lock() trolls rather than sleeps? Is there some other
sort of blocking going on in the loop that I'm not noticing? Here's the
relevant portion of io_lock() (in file inc/io.php):
$timeStart = time();
do {
//waited longer than 3 seconds? -> stale lock
if ((time() - $timeStart) > 3) break;
$locked = @mkdir($lockDir, $conf['dmode']);
if($locked && $conf['dperm']) chmod($lockDir, $conf['dperm']);
} while ($locked === false);
I wasn't able to find discussion of this issue in the archives.
Thinking that maybe usleep() wasn't sufficiently cross-platform, I did notice
that some Windows systems won't heed a microsecond resolution, but they'll
still heed usleep() to the nearest resolution, which is in the tens of
microsecs. Also, I noticed that Dokuwiki does use usleep in
lib/exe/indexer.php.
If we can use usleep() here, are there any other places where we might do the
same?
~joe
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