On Wed, 2011-12-28 at 06:17 +0100, Mike Galbraith wrote: > On Tue, 2011-12-27 at 10:20 +0100, Mike Galbraith wrote: > > Quoting removal commit af5ab277ded04bd9bc6b048c5a2f0e7d70ef0867 > > Historically, Linux has tried to make the regular timer tick on the > > various CPUs not happen at the same time, to avoid contention on > > xtime_lock. > > > > Nowadays, with the tickless kernel, this contention no longer happens > > since time keeping and updating are done differently. In addition, > > this skew is actually hurting power consumption in a measurable way on > > many-core systems. > > End quote > > Hm, nohz enabled, hogs burning up 60 of 64 cores. > > 56.11% [kernel] [k] ktime_get > 5.54% [kernel] [k] scheduler_tick > 4.02% [kernel] [k] cpuacct_charge > 3.78% [kernel] [k] __rcu_pending > 3.76% [kernel] [k] tick_sched_timer > 3.42% [kernel] [k] native_write_msr_safe > 1.58% [kernel] [k] run_timer_softirq > 1.28% [kernel] [k] __schedule > 1.21% [kernel] [k] apic_timer_interrupt > 1.07% [kernel] [k] _raw_spin_lock > 0.81% [kernel] [k] __switch_to > 0.67% [kernel] [k] thread_return > > Maybe skew-me wants to become a boot option? Yup.. or something. As above, but with skew. 3.06% [kernel] [k] ktime_get (Hm, wonder if nohz is usable now... nope. Tell nohz that isolated cores don't play balancer again, maybe it'll work now) -Mike -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
