linux-kernel - [PATCH 4/5] perf/powerpc: Count dropped samples in core-book3s PMU

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Message-ID: <20240905031027.2567913-5-namhyung@kernel.org>
Date: Wed,  4 Sep 2024 20:10:26 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>
Cc: Kan Liang <kan.liang@...ux.intel.com>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Stephane Eranian <eranian@...gle.com>,
	Ravi Bangoria <ravi.bangoria@....com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Naveen N Rao <naveen@...nel.org>,
	Kajol Jain <kjain@...ux.ibm.com>,
	Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
	linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH 4/5] perf/powerpc: Count dropped samples in core-book3s PMU

Due to the hardware limitation, sometimes it could sample kernel address
while attr.exclude_kernel is set.  In that case it silently drops the
sample.  Let's count that case in the new dropped_samples counter.

Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: Nicholas Piggin <npiggin@...il.com>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: Naveen N Rao <naveen@...nel.org>
Cc: Kajol Jain <kjain@...ux.ibm.com>
Cc: Athira Rajeev <atrajeev@...ux.vnet.ibm.com>
Cc: linuxppc-dev@...ts.ozlabs.org
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 arch/powerpc/perf/core-book3s.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index 42867469752d73cf..553e288b9f113836 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -2287,8 +2287,10 @@ static void record_and_restart(struct perf_event *event, unsigned long val,
 	 */
 	if (event->attr.exclude_kernel &&
 	    (event->attr.sample_type & PERF_SAMPLE_IP) &&
-	    is_kernel_addr(mfspr(SPRN_SIAR)))
+	    is_kernel_addr(mfspr(SPRN_SIAR))) {
+		atomic64_inc(&event->dropped_samples);
 		record = 0;
+	}
 
 	/*
 	 * Finally record data if requested.
-- 
2.46.0.469.g59c65b2a67-goog