Messages in this thread | | | Date | Mon, 10 Aug 2009 23:31:33 +0200 | From | Ingo Molnar <> | Subject | Re: 2.6.31-rc5 regression: x86 MCE malfunction on Thinkpad T42p |
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* Johannes Stezenbach <js@sig21.net> wrote:
> On Mon, Aug 10, 2009 at 10:14:06PM +0200, Ingo Molnar wrote: > > * Johannes Stezenbach <js@sig21.net> wrote: > > > > > > # ./perf stat true > > > > > > Performance counter stats for 'true': > > > > > > 0.985808 task-clock-msecs # 0.779 CPUs > > > 0 context-switches # 0.000 M/sec > > > 0 CPU-migrations # 0.000 M/sec > > > 110 page-faults # 0.112 M/sec > > > 583873 cycles # 592.279 M/sec > > > 500937 instructions # 0.858 IPC > > > <not counted> cache-references > > > <not counted> cache-misses > > > > > > 0.001265524 seconds time elapsed > > > > That looks almost normal - except for cache-references and > > cache-misses that is not counted. Could you send the /proc/cpuinfo > > info please? > > # cat /proc/cpuinfo > processor : 0 > vendor_id : GenuineIntel > cpu family : 6 > model : 13 > model name : Intel(R) Pentium(R) M processor 1.80GHz
ah, yes. There's no cache-references/misses, because in arch/x86/kernel/cpu/perf_counter.c we have two zero entries:
static const u64 p6_perfmon_event_map[] = { [PERF_COUNT_HW_CPU_CYCLES] = 0x0079, [PERF_COUNT_HW_INSTRUCTIONS] = 0x00c0, [PERF_COUNT_HW_CACHE_REFERENCES] = 0x0000, <---------- [PERF_COUNT_HW_CACHE_MISSES] = 0x0000, <---------- [PERF_COUNT_HW_BRANCH_INSTRUCTIONS] = 0x00c4, [PERF_COUNT_HW_BRANCH_MISSES] = 0x00c5, [PERF_COUNT_HW_BUS_CYCLES] = 0x0062, };
i.e. PERF_COUNT_HW_CACHE_REFERENCES and PERF_COUNT_HW_CACHE_MISSES is not filled in yet.
Could you try something like:
perf stat -e r0f2e true
(0x2e: L2 requests, 0x0f: all units)
if i checked the docs right that counter would give us L2 cache stats - does it display non-zero values?
> stepping : 6 > cpu MHz : 600.000 > cache size : 2048 KB > fdiv_bug : no > hlt_bug : no > f00f_bug : no > coma_bug : no > fpu : yes > fpu_exception : yes > cpuid level : 2 > wp : yes > flags : fpu vme de pse tsc msr mce cx8 apic sep mtrr pge mca cmov clflush dts acpi mmx fxsr sse sse2 ss tm pbe bts est tm2 > bogomips : 1196.15 > clflush size : 64 > power management: > > > > The warning is probably harmless - oprofile sampling still works > > fine, right? > > I haven't done much testing so far, but so far it looks promising. > > Could the warning be caused by the cpufreq ondemand governor? ISTR > that one should switch to the performance governor before doing > any profiling, but I forgot for this test.
there might be a connection - it could in theory cause sched_clock() transients and confuse the ring-buffer time-stamping.
Ingo
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