On Wed, Dec 12, 2018 at 10:50:30AM -0800, Andy Lutomirski wrote:
> As far as I know, RDTSCP gets the job done, as does LFENCE, RDTSC on
> Intel.
Same on AMD when LFENCE has been made dispatch-serializing.
> There was a big discussion a few years ago where we changed it
> from LFENCE;RDTSC;LFENCE to just LFENCE;RDTSC after everyone was
> reasonably convinced that the uarch would not dispatch two RDTSCs
> backwards if the first one was immediately preceeded by LFENCE.
Yeah, the second one won't pass the LFENCE so you won't see time going
backwards, sure.
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
