On Tue, 2007-05-29 at 13:28 -0700, Daniel Walker wrote:
> On Tue, 2007-05-29 at 14:52 +0200, Peter Zijlstra wrote:
> > + now = sched_clock();
> > + waittime = now - hlock->waittime_stamp;
> > +
>
> It looks like your using sched_clock() through out .. It's a little
> troubling considering the constraints on the function .. Most
> architecture implement a jiffies sched_clock() w/ 1 millisecond or worse
> resolution.. I'd imagine a millisecond hold time is pretty rare, even a
> millisecond wait time might be fairly rare too .. There's also no
> guarantee that sched_clock timestamps off two different cpu's can be
> compared (or at least that's my understanding) ..
All valid points, however.. calling anything more expensive 2-3 times
per lock acquisition is going to be _very_ painful.
Also, IMHO the contention count vs the acquisition count is the most
interesting number, the times are just a nice bonus (if and when they
work).
-
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