From: Peter Zijlstra <peterz@infradead.org>
To: "Liang, Kan" <kan.liang@intel.com>
Cc: "mingo@redhat.com" <mingo@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"eranian@google.com" <eranian@google.com>,
"alexander.shishkin@linux.intel.com"
<alexander.shishkin@linux.intel.com>,
"ak@linux.intel.com" <ak@linux.intel.com>,
"Odzioba, Lukasz" <lukasz.odzioba@intel.com>
Subject: Re: [PATCH] perf/x86: fix event counter update issue
Date: Tue, 29 Nov 2016 17:58:30 +0100 [thread overview]
Message-ID: <20161129165830.GM3092@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <37D7C6CF3E00A74B8858931C1DB2F07750CA4064@SHSMSX103.ccr.corp.intel.com>
On Tue, Nov 29, 2016 at 02:46:14PM +0000, Liang, Kan wrote:
> > And note that we _ALWAYS_ set the IN bits, even for !sampling events.
> > Also note we set max_period to (1<<31) - 1, so we should never exceed 31
> > bits.
> >
>
> The max_period is 0xfffffffff.
>
> The limit is breaked by this patch.
> 069e0c3c4058 ("perf/x86/intel: Support full width counting")
> https://patchwork.kernel.org/patch/2784191/
>
> /* Support full width counters using alternative MSR range */
> if (x86_pmu.intel_cap.full_width_write) {
> x86_pmu.max_period = x86_pmu.cntval_mask;
> x86_pmu.perfctr = MSR_IA32_PMC0;
> pr_cont("full-width counters, ");
> }
>
Wth do KNL/SLM have full_width_write set if they have short counters? I
should the whole point of the full_wdith thing was that in that case the
counters were actually 64bit wide.
next prev parent reply other threads:[~2016-11-29 16:58 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-28 19:26 [PATCH] perf/x86: fix event counter update issue kan.liang
2016-11-28 19:41 ` Stephane Eranian
2016-11-28 19:59 ` Liang, Kan
2016-11-28 20:18 ` Stephane Eranian
2016-11-28 20:23 ` Liang, Kan
2016-11-29 9:25 ` Peter Zijlstra
2016-11-29 14:46 ` Liang, Kan
2016-11-29 16:58 ` Peter Zijlstra [this message]
2016-11-29 17:06 ` Liang, Kan
2016-11-29 17:17 ` Peter Zijlstra
2016-11-29 17:20 ` Stephane Eranian
2016-11-29 17:30 ` Peter Zijlstra
2016-11-29 18:11 ` Stephane Eranian
2016-11-29 18:37 ` Andi Kleen
2016-11-29 19:07 ` Liang, Kan
2016-11-29 19:32 ` Peter Zijlstra
2016-11-29 20:33 ` Liang, Kan
2016-11-29 20:37 ` Stephane Eranian
2016-12-02 12:58 ` Odzioba, Lukasz
2016-12-05 10:25 ` Peter Zijlstra
2016-12-05 11:21 ` Odzioba, Lukasz
2017-02-22 14:49 ` Vince Weaver
2017-02-22 15:28 ` Liang, Kan
2017-02-22 19:18 ` Andi Kleen
2017-02-23 15:07 ` Vince Weaver
2017-02-23 16:14 ` Liang, Kan
2016-11-29 19:08 ` Odzioba, Lukasz
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