On 2014/5/27 21:20, Mike Galbraith wrote: > On Tue, 2014-05-27 at 20:50 +0800, Libo Chen wrote: > >> in my box: >> >> perf top -g --sort=symbol >> >> Events: 3K cycles >> 73.27% [k] read_hpet >> 4.30% [k] _raw_spin_lock_irqsave >> 1.88% [k] __schedule >> 1.00% [k] idle_cpu >> 0.91% [k] native_write_msr_safe >> 0.68% [k] select_task_rq_fair >> 0.51% [k] module_get_kallsym >> 0.49% [.] sem_post >> 0.44% [.] main >> 0.41% [k] menu_select >> 0.39% [k] _raw_spin_lock >> 0.38% [k] __switch_to >> 0.33% [k] _raw_spin_lock_irq >> 0.32% [k] format_decode >> 0.29% [.] usleep >> 0.28% [.] symbols__insert >> 0.27% [k] tick_nohz_stop_sched_tick >> 0.27% [k] update_stats_wait_end >> 0.26% [k] apic_timer_interrupt >> 0.25% [k] enqueue_entity >> 0.25% [k] sched_clock_local >> 0.24% [k] _raw_spin_unlock_irqrestore >> 0.24% [k] select_idle_sibling > > read_hpet? Are you booting box notsc or something? Migration cost is > the least of your worries.
oh yes, no tsc only hpet in my box. I don't know hhy is read_hpet is hot. but when I bind 3-th tasks to percpu,cost will be rapid decline, yet perf shows read_hpet is still hot. after bind Events: 561K cycles 64.18% [kernel] [k] read_hpet 5.51% usleep [.] main 2.71% [kernel] [k] __schedule 1.82% [kernel] [k] _raw_spin_lock_irqsave 1.56% libc-2.11.3.so [.] usleep 1.07% [kernel] [k] apic_timer_interrupt 0.89% libc-2.11.3.so [.] __GI___libc_nanosleep 0.82% [kernel] [k] native_write_msr_safe 0.82% [kernel] [k] ktime_get 0.71% [kernel] [k] trace_hardirqs_off 0.63% [kernel] [k] __switch_to 0.60% [kernel] [k] _raw_spin_unlock_irqrestore 0.47% [kernel] [k] menu_select 0.46% [kernel] [k] _raw_spin_lock 0.45% [kernel] [k] enqueue_entity 0.45% [kernel] [k] sched_clock_local 0.43% [kernel] [k] try_to_wake_up 0.42% [kernel] [k] hrtimer_nanosleep 0.36% [kernel] [k] do_nanosleep 0.35% [kernel] [k] _raw_spin_lock_irq 0.34% [kernel] [k] rb_insert_color 0.29% [kernel] [k] update_curr 0.29% [kernel] [k] native_sched_clock 0.28% [kernel] [k] hrtimer_interrupt 0.28% [kernel] [k] rcu_idle_exit_common 0.27% [kernel] [k] hrtimer_init 0.27% [kernel] [k] __hrtimer_start_range_ns 0.26% [kernel] [k] __rb_erase_color 0.26% [kernel] [k] lock_hrtimer_base 0.25% [kernel] [k] trace_hardirqs_on 0.23% [kernel] [k] rcu_idle_enter_common 0.23% [kernel] [k] cpuidle_idle_call 0.23% [kernel] [k] finish_task_switch 0.22% [kernel] [k] set_next_entity 0.22% [kernel] [k] cpuacct_charge 0.22% [kernel] [k] pick_next_task_fair 0.21% [kernel] [k] sys_nanosleep 0.20% [kernel] [k] rb_next 0.20% [kernel] [k] start_critical_timings > > -Mike > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
