[OpenAFS-devel] fileserver profiling

[Tom Keiser]

I've been profiling the pthreaded fileserver for a while now, and one
thing continues to bother me.  We call the time() syscall so
frequently that it's often 20% of our total execution time.
There are plenty of hacks to reduce this overhead, but every one I
know of will introduce some amount of non-determinism.  Is that an
acceptable risk?

Having a thread in a nanosleep; gettimeofday loop might be acceptable,
but during periods of high load, you couldn't guarantee that your
global epoch time variable would be _monotonically_ increasing.  I
suppose a combination of a SIGALRM handler and gettimeofday; setitimer
might mitigate that problem to some extent.  Anyone have any better
suggestions on how to reduce this overhead?

Certainly there are parts of the code that should continue to call
time() directly, but how much do we care if we accept a kerberos
ticket that expired a few milliseconds ago, when acceptable clock
drift is many orders of magnitude larger?

-- 
Tom Keiser
tkeiser@gmail.com