Messages in this thread | | | Date | Wed, 14 May 2008 08:00:06 +0200 | From | "Vegard Nossum" <> | Subject | Re: [BISECTED] Lots of "rescheduling IPIs" in powertop |
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On Tue, May 13, 2008 at 11:19 PM, Andi Kleen <andi@firstfloor.org> wrote: > > > The desktop is a P4: > > > > processor : 0 > > vendor_id : GenuineIntel > > cpu family : 15 > > model : 6 > > model name : Intel(R) Pentium(R) 4 CPU 3.00GHz > > stepping : 5 > > cpu MHz : 2992.624 > > cache size : 2048 KB > > > > flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge > > mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx > > lm constant_tsc pebs bts pni monitor ds_cpl est tm2 cid cx16 xtpr > > lahf_lm > > bogomips : 5990.81 > > clflush size : 64 > > > > (similar for processor 1) > > > > # msr > > 0 > > Ok the CPU reports it doesn't support any C states in MWAIT. If that is > correct then it would be correct to not use MWAIT idle and might > actually save more power to not use it. > > I don't know if that's true or not. Do you have a power meter perhaps? > If yes can you measure if there's a difference between mwait=idle / > default on your box when it is idle? > > [cc Arjan he might now if that CPU is supposed to support C1 in MWAIT]
No, sorry, no power meter :-/
> > The laptop is a Pentium Dual-Core: > > > > processor : 0 > > vendor_id : GenuineIntel > > cpu family : 6 > > model : 15 > > model name : Intel(R) Pentium(R) Dual CPU T2310 @ 1.46GHz > > stepping : 13 > > cpu MHz : 800.000 > > cache size : 1024 KB > ... > > > flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca > > cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe lm > > constant_tsc arch_perfmon pebs bts pni monitor ds_cpl est tm2 ssse3 > > cx16 xtpr lahf_lm > > bogomips : 2930.23 > > clflush size : 64 > > > > (similar for processor 1) > > > > # ./msr > > 1110 > > CPU reports it supports C1/C2/C3. Are you sure there is a difference on > that box? The code should have kept using MWAIT because it checks C1. > Please double check.
Yes, sorry, you are correct. I tested the idle=mwait only on the desktop machine (P4, msr = 0), and it improved the IPI problem. (I even rechecked right now, and it really does.)
Now I tested it on the laptop as well, and here it makes no difference.
Vegard
-- "The animistic metaphor of the bug that maliciously sneaked in while the programmer was not looking is intellectually dishonest as it disguises that the error is the programmer's own creation." -- E. W. Dijkstra, EWD1036
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