linux-kernel - [PATCH V6 06/14] perf/x86/intel: Use switch in intel_pmu_disable/enable

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Message-Id: <20200717140554.22863-7-kan.liang@linux.intel.com>
Date:   Fri, 17 Jul 2020 07:05:46 -0700
From:   kan.liang@...ux.intel.com
To:     peterz@...radead.org, acme@...hat.com, mingo@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     jolsa@...nel.org, eranian@...gle.com,
        alexander.shishkin@...ux.intel.com, ak@...ux.intel.com,
        Kan Liang <kan.liang@...ux.intel.com>
Subject: [PATCH V6 06/14] perf/x86/intel: Use switch in intel_pmu_disable/enable_event

From: Kan Liang <kan.liang@...ux.intel.com>

Many items are checked in the intel_pmu_disable/enable_event. More items
will be added later, e.g. perf metrics events.

Use switch, which is more efficient, to replace the if-else.

If the idx is invalid, print a warning.

For the case INTEL_PMC_IDX_FIXED_BTS in intel_pmu_disable_event, don't
need to check the event->attr.precise_ip. Use return for the case.

Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
---
 arch/x86/events/intel/core.c | 36 ++++++++++++++++++++++++++++--------
 1 file changed, 28 insertions(+), 8 deletions(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index ac1408fe1aee..2b1701c08f46 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -2180,17 +2180,28 @@ static void intel_pmu_disable_event(struct perf_event *event)
 	struct hw_perf_event *hwc = &event->hw;
 	int idx = hwc->idx;
 
-	if (idx < INTEL_PMC_IDX_FIXED) {
+	switch (idx) {
+	case 0 ... INTEL_PMC_IDX_FIXED - 1:
 		intel_clear_masks(event, idx);
 		x86_pmu_disable_event(event);
-	} else if (idx < INTEL_PMC_IDX_FIXED_BTS) {
+		break;
+	case INTEL_PMC_IDX_FIXED ... INTEL_PMC_IDX_FIXED_BTS - 1:
 		intel_clear_masks(event, idx);
 		intel_pmu_disable_fixed(event);
-	} else if (idx == INTEL_PMC_IDX_FIXED_BTS) {
+		break;
+	case INTEL_PMC_IDX_FIXED_BTS:
 		intel_pmu_disable_bts();
 		intel_pmu_drain_bts_buffer();
-	} else if (idx == INTEL_PMC_IDX_FIXED_VLBR)
+		return;
+	case INTEL_PMC_IDX_FIXED_VLBR:
 		intel_clear_masks(event, idx);
+		break;
+	default:
+		intel_clear_masks(event, idx);
+		pr_warn("Failed to disable the event with invalid index %d\n",
+			idx);
+		return;
+	}
 
 	/*
 	 * Needs to be called after x86_pmu_disable_event,
@@ -2262,18 +2273,27 @@ static void intel_pmu_enable_event(struct perf_event *event)
 	if (unlikely(event->attr.precise_ip))
 		intel_pmu_pebs_enable(event);
 
-	if (idx < INTEL_PMC_IDX_FIXED) {
+	switch (idx) {
+	case 0 ... INTEL_PMC_IDX_FIXED - 1:
 		intel_set_masks(event, idx);
 		__x86_pmu_enable_event(hwc, ARCH_PERFMON_EVENTSEL_ENABLE);
-	} else if (idx < INTEL_PMC_IDX_FIXED_BTS) {
+		break;
+	case INTEL_PMC_IDX_FIXED ... INTEL_PMC_IDX_FIXED_BTS - 1:
 		intel_set_masks(event, idx);
 		intel_pmu_enable_fixed(event);
-	} else if (idx == INTEL_PMC_IDX_FIXED_BTS) {
+		break;
+	case INTEL_PMC_IDX_FIXED_BTS:
 		if (!__this_cpu_read(cpu_hw_events.enabled))
 			return;
 		intel_pmu_enable_bts(hwc->config);
-	} else if (idx == INTEL_PMC_IDX_FIXED_VLBR)
+		break;
+	case INTEL_PMC_IDX_FIXED_VLBR:
 		intel_set_masks(event, idx);
+		break;
+	default:
+		pr_warn("Failed to enable the event with invalid index %d\n",
+			idx);
+	}
 }
 
 static void intel_pmu_add_event(struct perf_event *event)
-- 
2.17.1