linux-kernel - [PATCH V3 1/5] perf/x86/intel/uncore: customized pmu event read for client IMC uncore

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Date:   Tue, 24 Oct 2017 04:05:20 -0700
From:   kan.liang@...el.com
To:     tglx@...utronix.de, peterz@...radead.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org
Cc:     acme@...nel.org, eranian@...gle.com, ak@...ux.intel.com,
        Kan Liang <Kan.liang@...el.com>
Subject: [PATCH V3 1/5] perf/x86/intel/uncore: customized pmu event read for client IMC uncore

From: Kan Liang <Kan.liang@...el.com>

The client IMC uncore obscurely hack the generic
uncore_perf_event_update to support the 'UNCORE_PMC_IDX_FIXED + 1' case.
The code quality issue will bring problem when new counter index is
introduced into generic code. For example, free running counter.

Introduce customized pmu event_read function for client IMC uncore.
The customized function is exactly copied from previous generic
uncore_pmu_event_read.

Correct the fixed counter checking code in uncore_perf_event_update.

Signed-off-by: Kan Liang <Kan.liang@...el.com>
---

Change since V2:
 - New patch to fix event->hw.idx >= UNCORE_PMC_IDX_FIXED in generic code.
   Temporarily add customized pmu event_read function. Patch 5/5 will clean up
   the customized event_* functions for client IMC uncore

 arch/x86/events/intel/uncore.c     |  2 +-
 arch/x86/events/intel/uncore_snb.c | 26 +++++++++++++++++++++++++-
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
index 1c5390f..3b8cd88 100644
--- a/arch/x86/events/intel/uncore.c
+++ b/arch/x86/events/intel/uncore.c
@@ -218,7 +218,7 @@ void uncore_perf_event_update(struct intel_uncore_box *box, struct perf_event *e
 	u64 prev_count, new_count, delta;
 	int shift;
 
-	if (event->hw.idx >= UNCORE_PMC_IDX_FIXED)
+	if (event->hw.idx == UNCORE_PMC_IDX_FIXED)
 		shift = 64 - uncore_fixed_ctr_bits(box);
 	else
 		shift = 64 - uncore_perf_ctr_bits(box);
diff --git a/arch/x86/events/intel/uncore_snb.c b/arch/x86/events/intel/uncore_snb.c
index db1127c..9d5cd3f 100644
--- a/arch/x86/events/intel/uncore_snb.c
+++ b/arch/x86/events/intel/uncore_snb.c
@@ -498,6 +498,30 @@ static void snb_uncore_imc_event_del(struct perf_event *event, int flags)
 	snb_uncore_imc_event_stop(event, PERF_EF_UPDATE);
 }
 
+static void snb_uncore_imc_event_read(struct perf_event *event)
+{
+	struct intel_uncore_box *box = uncore_event_to_box(event);
+	u64 prev_count, new_count, delta;
+	int shift;
+
+	if (event->hw.idx >= UNCORE_PMC_IDX_FIXED)
+		shift = 64 - uncore_fixed_ctr_bits(box);
+	else
+		shift = 64 - uncore_perf_ctr_bits(box);
+
+	/* the hrtimer might modify the previous event value */
+again:
+	prev_count = local64_read(&event->hw.prev_count);
+	new_count = uncore_read_counter(box, event);
+	if (local64_xchg(&event->hw.prev_count, new_count) != prev_count)
+		goto again;
+
+	delta = (new_count << shift) - (prev_count << shift);
+	delta >>= shift;
+
+	local64_add(delta, &event->count);
+}
+
 int snb_pci2phy_map_init(int devid)
 {
 	struct pci_dev *dev = NULL;
@@ -533,7 +557,7 @@ static struct pmu snb_uncore_imc_pmu = {
 	.del		= snb_uncore_imc_event_del,
 	.start		= snb_uncore_imc_event_start,
 	.stop		= snb_uncore_imc_event_stop,
-	.read		= uncore_pmu_event_read,
+	.read		= snb_uncore_imc_event_read,
 };
 
 static struct intel_uncore_ops snb_uncore_imc_ops = {
-- 
2.7.4