On Tue, Nov 06, 2012 at 12:24:20PM -0800, Steve Muckle wrote: > On 11/05/12 01:15, Russell King - ARM Linux wrote: > > On Mon, Nov 05, 2012 at 09:23:38AM +0530, Taniya Das wrote: > >> I was looking at the arch/arm/process.c:cpu_die, I was wondering why we > >> do not exit from NOHZ for a hotplugged/offline cpu? > > > > Offlined CPUs are not supposed to just 'return' from cpu_die(), and > > in actual fact they can't. > > Although an offline CPU will not come back into the idle thread by > returning from cpu_die(), I believe the question about exiting nohz mode > before cpu_die() still stands. Well, that depends on the design of all that. I don't know that, but what I do know is we're doing exactly the same as x86 which I presume is correct. > >From arch/arm/process.c:cpu_idle() it appears a CPU could enter > pm_idle() for a while (in nohz mode), then execute the inner loop again > and call cpu_die(). Is there the potential for cpu idle time accounting > to get messed up here by not exiting nohz mode prior to the cpu dying, > so that missed ticks from nohz are properly accounted for? Why does the idle time matter if the CPU has been taken offline? In any case, I think this is a question for the CPU idle people; it's not a feature that I've ever knowingly used or have any interest in using at the moment. -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
