On Fri, 2015-08-21 at 23:30 +0800, Julian Elischer wrote: > On 8/21/15 11:25 PM, Adrian Chadd wrote: > > Ah, cool. I'll give it a whirl. > > > > I'm a little worried about having all of the other cores spinning in > > this case (mostly thermal; the machines get VERY LOUD when the CPUs > > are spinning..) > > > make each spin with the pause instruction.. and for N seconds (N being > the CPU ID) or something
cpu_spinwait() is defined as ia32_pause() on i386 and amd64. The problem is that ONLY x86 arches benefit from cpu_spinwait(), it's just a nop on other arches, which turn into little radiant heaters for long spins (like while waiting for APs to be released). On ARM we have a really nice wait-for-event/signal-event pair of instructions, where WFE would be a natural for cpu_spinwait(), but would require a matching cpu_spinwake() type call to be sprinkled around to do the matching SEV instruction. -- Ian _______________________________________________ freebsd-current@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
