* Ingo Molnar <mingo@xxxxxxx> wrote: > one thing to check would be whether both kernels use the same > clocksource, via: > > cat /sys/devices/system/clocksource/clocksource0/current_clocksource > > but at first sight there's no clocksource related overhead in the > oprofile. i've started a similar netperf test and clocksource overhead dominates the profile: 5553 handle_fasteoi_irq 26.1934 5940 nv_start_xmit_optimized 6.6892 6014 ack_ioapic_quirk_irq 44.5481 7591 mask_IO_APIC_irq 154.9184 8155 __copy_from_user_ll 37.4083 13371 io_apic_base 417.8438 13565 get_next_timer_interrupt 29.7478 13966 __modify_IO_APIC_irq 151.8043 14213 do_irqd 22.7045 17834 unmask_IO_APIC_irq 424.6190 20503 __schedule 6.4455 48456 cpu_idle 180.8060 170001 acpi_pm_read 8947.4211 517107 total 0.1566 acpi_pm_read() amounts to 32% overhead! i'm not sure why the oprofile results show no clocksource overhead - the -rt kernel typically uses the pm-timer on Opterons. to get more comparable results, boot the vanilla kernel with the "apicpmtimer" boot option, and/or do this after bootup: echo acpi_pm > /sys/devices/system/clocksource/clocksource0/current_clocksource Ingo - 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
