Messages in this thread | | | Date | Sun, 03 May 2009 08:06:55 +0200 | From | Eric Dumazet <> | Subject | Re: [BUG] perf_counter: change cpu frequencies |
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Eric Dumazet a écrit : > 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 :) >
Update :
Mike Galbraith suggested me to try various things, and finally, I discovered this frequency change was probably a BIOS problem on my HP BL460c G1
System Options -> Power regulator for Proliant
[*] HP Dynamic Power Savings Mode [ ] HP Static Low Power Mode [ ] HP Static High Performance Mode [ ] OS Control Mode
I switched it to 'OS Control Mode'
Then acpi-cpufreq could load, and no more frequencies changes on a "perf -a sleep 10" session, using or not cpufreq. (Supported cpufreq speeds on these cpus : 1999 & 2999 MHz)
So it was a BIOS issue
# perf stat -a sleep 10
Performance counter stats for 'sleep':
80005.418223 task clock ticks (msecs) 80266 context switches (events) 3 CPU migrations (events) 486 pagefaults (events) 240013851624 CPU cycles (events) << good >> 239076501419 instructions (events) 679464 cache references (events) <not counted> cache misses
Wall-clock time elapsed: 10000.468808 msecs
Thank you
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