Messages in this thread | | | Date | Tue, 23 Jun 2009 11:19:59 +0200 | Subject | Re: perf_counter Atom patch | From | stephane eranian <> |
| |
On Tue, Jun 23, 2009 at 10:53 AM, Yong Wang<yong.y.wang@linux.intel.com> wrote: > On Tue, Jun 23, 2009 at 10:40:45AM +0200, stephane eranian wrote: >> Yong, >> >> On Tue, Jun 23, 2009 at 10:27 AM, stephane >> eranian<eranian@googlemail.com> wrote: >> > Hi, >> > >> > On Tue, Jun 23, 2009 at 9:59 AM, Yong Wang<yong.y.wang@linux.intel.com> wrote: >> >> On Tue, Jun 23, 2009 at 09:45:03AM +0200, stephane eranian wrote: >> >>> >> >>> Unfortunately, I don't have a N270 to compare with your results. >> >>> We need to verify whether or not N270 implements the fixed counters. >> >>> Does it report architected perfmon v3 or v1? >> >>> >> >> >> >> All Atom processors report perfmon v3 as specified in SDM. N270 is no >> >> exception. >> >> >> > V3 does not set a minimal number of fixed counters, could be zero. But >> > that seems >> > odd. Let me ask around. >> > >> Second thought on this: >> x86_pmu.num_counters_fixed = >> max((int)edx.split.num_counters_fixed, 3); >> >> rdmsrl(MSR_CORE_PERF_GLOBAL_CTRL, x86_pmu.intel_ctrl); >> >> >> Forcing num_counter_fixed is not enough, you need to make sure they are actually >> activated in GLOBAL_CTRL, i.e., make sure bits 32-34 are set in intel_ctrl. >> Depending on which machine you're on, the power on value for GLOBAL_CTRL >> changes. The correct value for it should be that ONLY generic counters are on >> by default. >> > > Oh, this might be why fixed counter do not work on my Atom box. I will > look into it. BTW, why should ONLY generic counters be on by default? > Glad you asked. I think, it's for backward compatibility with processors such as Core Duo with architected perfmon v1 which did not have the GLOBAL_* controls. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |