[OpenAFS-devel] fileserver profiling

[Kyle Moffett]

On Mar 13, 2005, at 14:32, Tom Keiser wrote:
> ok.  I've been operating under the assumption that implementing a
> purely userspace gettimeofday would be too costly, but apparently that
> assumption is false.  If you're only storing seconds since the epoch,
> your value is atomic, so you don't need sanity checking to prevent
> time apparently going backwards.

Agreed (Although that's somewhat architecture and compiler dependent).

> I agree that if you're going to store usecs too, then you need the
> read barriers.  When I said we could coalesce ops and reduce the
> number of barriers, I was thinking about a technique similar to RCU
> that Herlihy discussed back in the late 80's

Interesting.  In any case, it's very efficient to do both time() and
gettimeofday() in userspace without using much CPU time.

>> My goal for this implementation

Hrm, I appear to have inadvertently deleted a paragraph or two from
my response in that email, oops!

Cheers,
Kyle Moffett

-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GCM/CS/IT/U d- s++: a18 C++++>$ UB/L/X/*++++(+)>$ P+++(++++)>$
L++++(+++) E W++(+) N+++(++) o? K? w--- O? M++ V? PS+() PE+(-) Y+
PGP+++ t+(+++) 5 X R? tv-(--) b++++(++) DI+ D+ G e->++++$ h!*()>++$ r  
!y?(-)
------END GEEK CODE BLOCK------