Performance of 4.x vs 5.x (Re: Lifetime of FreeBSD branches)
jd at ugcs.caltech.edu
Wed May 25 16:03:07 PDT 2005
It's different, yes. But the trouble is that you need a controlled
interrupt source--i.e., you have to have some concept of when an "event"
might have been handled (were it not for such and such activity).
I posit that without that counterfactual talking about PREEMPTION is
The technique I mentioned--measuring and comparing the jitter was intended
to quash measuring the performance of the network stack itself.
Do you have an idea how you can pose that counterfactual in a synthetic
arrangement more closely connected with the problem at hand?
On Wed, 25 May 2005, Kris Kennaway wrote:
> On Wed, May 25, 2005 at 03:33:39PM -0700, Jon Dama wrote:
> > Could this be quantified by setting up a synthetic experiement:
> > 1) one machine uses dummynet to generate a uniform packet/sec stream
> > 2) another machine has a process receiving those packets and recording
> > their arrival relative to the local TSC. afaik, the TSC is the only
> > source of wall-time that doesn't involve a system call. Is that right?
> > Are the TSCs synchronized on SMP systems?
> > 3) Generate another source of activity on the receiving machine to
> > estimate the effect of PREEMPTION relative to the (lack of) quiescence.
> > 4) use the jitter in the TSC deltas to infer the effect of preemption
> That would be attempting to benchmark something entirely different.
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