Messages in this thread | | | Date | Thu, 18 Nov 2004 16:44:42 +0100 | From | Ingo Molnar <> | Subject | Re: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm1-V0.7.27-10 |
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* Adam Heath <adam@doogie.org> wrote:
> Running .26-5. Been running almost 2 days. All small latency values. > Then, just a few minutes ago, got a 133us value:
this entry has most of the overhead:
> 0 80000000 00000004 [0284618592175975] 0.000ms (+0.000ms): preempt_schedule+0x11/0x80 <c02bbb81> (__do_IRQ+0x13d/0x170 <c013f3cd>) > 0 80000000 00000005 [0284618592176118] 0.000ms (+0.127ms): irq_exit+0xb/0x50 <c013f10b> (do_IRQ+0x53/0x70 <c01080d3>) > 0 80000000 00000006 [0284618592387634] 0.127ms (+0.000ms): do_IRQ+0x0/0x70 <c0108080> (<0000a253>) > 0 80000000 00000007 [0284618592387690] 0.127ms (+0.000ms): do_IRQ+0x0/0x70 <c0108080> (<0000000e>)
this shows that we interrupted some longer critical section - in this case it seems to be BIOS/APM code.
> Note the jump in irq_exit/do_IRQ.
that jump is a delayed interrupt hitting the BIOS on its way out of APM idle mode it seems:
> 0 80000000 0000001b [0284618592393899] 0.131ms (+0.000ms): apm_do_busy+0xb/0x40 <c01111eb> (cpu_idle+0x4c/0x70 <c0103f9c>) > 0 80000000 0000001c [0284618592393987] 0.131ms (+0.000ms): apm_bios_call_simple+0xe/0xf0 <c0110f2e> (apm_do_busy+0x2e/0x40 <c011120e>)
There's nothing to be done about that, except to disable APM. Perhaps you could try ACPI, maybe that doesnt have such latencies in the BIOS.
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