There are a couple of performance bug fixes in trunk and 2.7 branch now
that I thought might be of interest to the list.
The first went in about two weeks ago and fixed a condition variable bug
inside of the trove testcontext() function. There was a race condition
where it was possible for operations to complete without waking up the
caller, therefore causing the function to sleep longer than it should have.
I don't know how hard it was to trigger in general, but I was able to
see it on SMP servers with default sync coalescing and a large number of
concurrent metadata modifications. I was testing it with an artificial
benchmark that emulated 10,000 concurrent creates on a server without
network traffic, and fixing this bug improved the overall performance of
this scenario by a factor of 16. Hopefully some of this will translate
into real world improvement if you have a big concurrent metadata workload.
The second bug fix just went in this week. The problem was basically
some leftover (and very slow) deprecated code in the trove list_attr()
function used by readdirplus(). It showed up in the pvfs2-lsplus
command line utility, which was supposed to be a much faster version of
ls (particularly with -l), but actually ran slower than pvfs2-ls for
many cases.
At any rate, this list_attr() problem is fixed now as well. The result
is that it sped up the pvfs2-lsplus by at least a factor of 4 for the
cases that I was looking at with thousands of files on a single server.
pvfs2-lsplus is definitely a big improvement now if you need a fast
way to list files.
-Phil
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