[OpenAFS-devel] fileserver profiling

[Derrick J Brashear]

On Thu, 3 Mar 2005, Troy Benjegerdes wrote:

> I don't see how you'd ever get a clock that goes backwards with this
> method.. it might not increase under high load, but would that be a
> problem?

We have had a multiprocessor Linux system where the clock went backwards 
without the help of ntp during normal operation.

> Can we set the "time" thread to real-time priority? Or can we set up a
> small chunk (say 4k) of System-V shared memory (or mmap-ed file) that
> can be updated at some configurable rate (1hz to 100hz maybe) by a process
> with real-time priority? All the AFS processes (not just the fileserver)
> would then map that memory read-only.

sysv shared memory will have portability issues. mmap() is probably 
better. but lwp dealt by having an approxtime and a time call, and if you 
needed a real time, you asked, and if you didn't you used the cached time.
e.g. we already had a hack.