linux-kernel - Re: [PATCH -v3] perf, x86: try to handle unknown nmis with running perfctrs

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Date:	Thu, 19 Aug 2010 16:27:13 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Don Zickus <dzickus@...hat.com>
Cc:	Robert Richter <robert.richter@....com>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Lin Ming <ming.m.lin@...el.com>, Ingo Molnar <mingo@...e.hu>,
	"fweisbec@...il.com" <fweisbec@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Huang, Ying" <ying.huang@...el.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH -v3] perf, x86: try to handle unknown nmis with running
 perfctrs

On Thu, 2010-08-19 at 10:12 -0400, Don Zickus wrote:
> On Thu, Aug 19, 2010 at 12:45:53PM +0200, Peter Zijlstra wrote:
> > 
> > I queued it with that part changed to:
> 
> I realized the other day this change doesn't cover the nehalem, core and p4
> cases which use
> 
> intel_pmu_handle_irq
> p4_pmu_handle_irq
> 
> as their handlers.  Though that patch can go on top of Robert's.

Something like this?

---
Index: linux-2.6/arch/x86/kernel/cpu/perf_event_intel.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/perf_event_intel.c
+++ linux-2.6/arch/x86/kernel/cpu/perf_event_intel.c
@@ -713,6 +713,7 @@ static int intel_pmu_handle_irq(struct p
 	struct cpu_hw_events *cpuc;
 	int bit, loops;
 	u64 ack, status;
+	int handled = 0;
 
 	perf_sample_data_init(&data, 0);
 
@@ -743,12 +744,16 @@ again:
 	/*
 	 * PEBS overflow sets bit 62 in the global status register
 	 */
-	if (__test_and_clear_bit(62, (unsigned long *)&status))
+	if (__test_and_clear_bit(62, (unsigned long *)&status)) {
+		handled++;
 		x86_pmu.drain_pebs(regs);
+	}
 
 	for_each_set_bit(bit, (unsigned long *)&status, X86_PMC_IDX_MAX) {
 		struct perf_event *event = cpuc->events[bit];
 
+		handled++;
+
 		if (!test_bit(bit, cpuc->active_mask))
 			continue;
 
@@ -772,7 +777,7 @@ again:
 
 done:
 	intel_pmu_enable_all(0);
-	return 1;
+	return handled;
 }
 
 static struct event_constraint *
Index: linux-2.6/arch/x86/kernel/cpu/perf_event_p4.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/perf_event_p4.c
+++ linux-2.6/arch/x86/kernel/cpu/perf_event_p4.c
@@ -673,7 +673,7 @@ static int p4_pmu_handle_irq(struct pt_r
 		if (!overflow && (val & (1ULL << (x86_pmu.cntval_bits - 1))))
 			continue;
 
-		handled += overflow;
+		handled += !!overflow;
 
 		/* event overflow for sure */
 		data.period = event->hw.last_period;
@@ -690,7 +690,7 @@ static int p4_pmu_handle_irq(struct pt_r
 		inc_irq_stat(apic_perf_irqs);
 	}
 
-	return handled > 0;
+	return handled;
 }
 
 /*

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