linux-kernel - [PATCH v2] Powerpc/perf: Wire up PMI throttling

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Date:   Wed, 21 Nov 2018 09:26:37 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
To:     mpe@...erman.id.au, linuxppc-dev@...ts.ozlabs.org
Cc:     benh@...nel.crashing.org, paulus@...ba.org, ebiederm@...ssion.com,
        muriloo@...ux.ibm.com, christophe.leroy@....fr, npiggin@...il.com,
        leitao@...ian.org, aneesh.kumar@...ux.vnet.ibm.com,
        linux-kernel@...r.kernel.org, naveen.n.rao@...ux.vnet.ibm.com,
        maddy@...ux.vnet.ibm.com,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Subject: [PATCH v2] Powerpc/perf: Wire up PMI throttling

Commit 14c63f17b1fde ("perf: Drop sample rate when sampling is too
slow") introduced a way to throttle PMU interrupts if we're spending
too much time just processing those. Wire up powerpc PMI handler to
use this infrastructure.

We have throttling of the *rate* of interrupts, but this adds
throttling based on the *time taken* to process the interrupts.

Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
---
v1: https://lkml.org/lkml/2018/11/14/627

 arch/powerpc/perf/core-book3s.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index 81f8a0c838ae..3cd2ec9c9732 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -10,6 +10,7 @@
  */
 #include <linux/kernel.h>
 #include <linux/sched.h>
+#include <linux/sched/clock.h>
 #include <linux/perf_event.h>
 #include <linux/percpu.h>
 #include <linux/hardirq.h>
@@ -2148,7 +2149,7 @@ static bool pmc_overflow(unsigned long val)
 /*
  * Performance monitor interrupt stuff
  */
-static void perf_event_interrupt(struct pt_regs *regs)
+static void __perf_event_interrupt(struct pt_regs *regs)
 {
 	int i, j;
 	struct cpu_hw_events *cpuhw = this_cpu_ptr(&cpu_hw_events);
@@ -2232,6 +2233,14 @@ static void perf_event_interrupt(struct pt_regs *regs)
 		irq_exit();
 }
 
+static void perf_event_interrupt(struct pt_regs *regs)
+{
+	u64 start_clock = sched_clock();
+
+	__perf_event_interrupt(regs);
+	perf_sample_event_took(sched_clock() - start_clock);
+}
+
 static int power_pmu_prepare_cpu(unsigned int cpu)
 {
 	struct cpu_hw_events *cpuhw = &per_cpu(cpu_hw_events, cpu);
-- 
2.17.1