Messages in this thread | | | Date | Tue, 13 May 2008 23:19:47 +0200 | From | Andi Kleen <> | Subject | Re: [BISECTED] Lots of "rescheduling IPIs" in powertop |
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> 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]
> > 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.
-Andi
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