Kyle Moffett wrote:
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.
The question is how many dentries are cached at the time? And it looks
like you are just renaming, not moving, so there would be no need to
recompute the acls at all.
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