Messages in this thread | | | Date | Sat, 28 Nov 2009 13:10:21 -0500 | From | Michael Breuer <> | Subject | Re: Problem? intel_iommu=off; perf top shows acpi_os_read_port as extremely busy |
| |
Ok - my only question then is why things appear so different with intel_iommu enabled. Arjan van de Ven wrote: > On Sat, 28 Nov 2009 08:18:08 +0100 > Ingo Molnar <mingo@elte.hu> wrote: > > >> * Michael Breuer <mbreuer@majjas.com> wrote: >> >> >>> Having given up for now on VT-D, I rebooted 2.6.38 rc8 with >>> intel_iommu=off. Whilst my myriad of broken bios issues cleared, I >>> now see in perf top acpi_os_read_port as continually the busiest >>> function. With intel_iommu enabled, _spin_lock was always on top, >>> and nothing else was notable. >>> >>> This seems odd to me, perhaps this will make sense to someone else. >>> >>> FWIW, I'm running on an Asus p6t deluxe v2; ht enabled; no errors >>> or oddities in dmesg or /var/log/messages. >>> >> Could you post the perf top output please? >> >> Also, could you also post the output of: >> >> perf stat -a --repeat 10 sleep 1 >> >> this will show us how idle the system is. (My guess is that your >> system is idle and perf top shows acpi_os_read_port because the >> system goes to idle via ACPI methods and PIO is slow. In that case >> all is nominal and your system is fine. But it's hard to tell without >> more details.) >> >> > > yeah the os_read_port is part of the idle loop, so if your system is > idle it'll show up big.... not much we can optimize there though... > -- > 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/ >
| |