Re: Performance overhead of get_cycles_sync

Ingo Molnar
2007-12-11T17:04:18Z

* Arjan van de Ven <arjan@infradead.org> wrote:

> > * Dor Laor <dor.laor@gmail.com> wrote:
> >
> > The patch below should resolve this - could you please test and Ack
> > it? But this CPUID was present in v2.6.23 too, so why did it only
> > show up in 2.6.24-rc for you?
>
> isn't this probably wrong since this code is also used in the vsyscall
> code..

the TSC clocksource (and hence the vsyscall code) is turned off on
systems that fail the TOD/CLOCK portion of this test:

http://people.redhat.com/mingo/time-warp-test/time-warp-test.c

i.e. on the majority of systems in place.

Ingo