On Wed, 2011-12-28 at 14:35 +0100, Arjan van de Ven wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 12/28/2011 6:17 AM, 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? > > this is 56% of kernel time.. of how much total time? To answer the question.. 99.57% burn [.] main 0.14% [kernel] [k] ktime_get That's the DL980 running a 250Hz kernel. Dinky, but for my picky RT load, too much nonetheless. (hm, what would SGI monster box say?) -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
