Messages in this thread | | | Date | Thu, 30 Apr 2009 18:07:44 +0200 | From | Eric Dumazet <> | Subject | [BUG] perf_counter: change cpu frequencies |
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Eric Dumazet a écrit :
> But if I use plain "perf stat -a sleep 10" > it seems I get wrong values again (16 G cycles/sec) for all next perf sessions >
Well, I confirm all my cpus switched from 3GHz to 2GHz, after
"perf stat -a sleep 10"
(but "perf stat -e instructions -e cycles -a sleep 10" doesnt trigger this problem)
Nothing logged, and /proc/cpuinfo stills reports 3 GHz frequencies
# cat unit.c main() { int i; for (i = 0 ; i < 10000000; i++) getppid(); } # time ./unit
real 0m0.818s user 0m0.289s sys 0m0.529s # perf stat -a sleep 10 2>/dev/null # time ./unit
real 0m1.122s user 0m0.482s sys 0m0.640s
# tail -n 27 /proc/cpuinfo processor : 7 vendor_id : GenuineIntel cpu family : 6 model : 23 model name : Intel(R) Xeon(R) CPU E5450 @ 3.00GHz stepping : 6 cpu MHz : 3000.102 cache size : 6144 KB physical id : 1 siblings : 1 core id : 3 cpu cores : 4 apicid : 7 initial apicid : 7 fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 10 wp : yes 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 lm constant_tsc arch_perfmon pebs bts pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 lahf_lm tpr_shadow vnmi flexpriority bogomips : 6000.01 clflush size : 64 power management:
# grep CPU_FREQ .config # CONFIG_CPU_FREQ is not set
perf_counter seems promising, but still... needs some bug hunting :)
Thank you
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