Messages in this thread | | | From | KOSAKI Motohiro <> | Date | Thu, 26 Jan 2012 16:25:42 -0500 | Subject | Re: [PATCH] Avoid mask based num_possible_cpus and num_online_cpus -v4 |
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2012/1/26 Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>: > On 01/25/2012 04:55 AM, Venkatesh Pallipadi wrote: > >> Kernel's notion of possible cpus (from include/linux/cpumask.h) >> * cpu_possible_mask- has bit 'cpu' set iff cpu is populatable >> >> * The cpu_possible_mask is fixed at boot time, as the set of CPU id's >> * that it is possible might ever be plugged in at anytime during the >> * life of that system boot. >> >> #define num_possible_cpus() cpumask_weight(cpu_possible_mask) >> >> and on x86 cpumask_weight() calls hweight64 and hweight64 (on older kernels >> and systems with !X86_FEATURE_POPCNT) or a popcnt based alternative. >> >> i.e, We needlessly go through this mask based calculation everytime >> num_possible_cpus() is called. >> >> The problem is there with cpu_online_mask() as well, which is fixed value at >> boot time in !CONFIG_HOTPLUG_CPU case and should not change that often even >> in HOTPLUG case. >> >> Though most of the callers of these two routines are init time (with few >> exceptions of runtime calls), it is cleaner to use variables >> and not go through this repeated mask based calculation. >> >> Signed-off-by: Venkatesh Pallipadi <venki@google.com> >> --- > > > Looks good to me now :-) > > Acked-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
I'm ok too.
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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