On Aug 17, 2007, at 15:01:48, Phillip Susi wrote:
[email protected] wrote:It will become even *more* of a "not that common" if the lock will block moves and ACL changes *across the filesystem* for potentially *minutes* at a time.It will not take anywhere NEAR minutes at a time to update the in memory dentries, more like 50ms.
One last comment:50ms to update in-memory dentries would be FRIGGING TERRIBLE!!! Using Perl, an interpreted language, the following script takes 3.39s to run on one of my lower-end systems:
for (0 .. 10000) {
mkdir "a-$_";
mkdir "b-$_";
rename "a-$_", "b-$_";
}
It's not even deleting things afterwards so it's populating a
directory with ten thousand entries. We can easily calculate
10,000/3.39 = 2,949 entries per second, or 0.339 milliseconds per entry.
When I change it to rmdir things instead, the runtime goes down to 2.89s == 3460 entries/sec == 0.289 milliseconds per entry.
If such a scheme even increases the overhead of a directory rename by a hundredth of a millisecond on that box it would easily be a 2-3% performance hit. Given that people tend to kill for 1% performance boosts, that's not likely to be a good idea.
Cheers, Kyle Moffett - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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