Messages in this thread | | | Date | Sat, 28 Nov 2009 09:45:30 -0800 | From | Arjan van de Ven <> | Subject | Re: Problem? intel_iommu=off; perf top shows acpi_os_read_port as extremely busy |
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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...
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