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From: Peter Zijlstra <peterz@infradead.org>
To: mingo@kernel.org, tglx@linutronix.de, rostedt@goodmis.org
Cc: linux-kernel@vger.kernel.org, kan.liang@linux.intel.com,
	acme@kernel.org, mark.rutland@arm.com,
	alexander.shishkin@linux.intel.com, jolsa@redhat.com,
	namhyung@kernel.org, ak@linux.intel.com, eranian@google.com,
	peterz@infradead.org, Jesper Dangaard Brouer <brouer@redhat.com>
Subject: [PATCH 4/6] perf: Optimize get_recursion_context()
Date: Fri, 30 Oct 2020 16:13:49 +0100
Message-ID: <20201030151955.187580298@infradead.org> (raw)
In-Reply-To: <20201030151345.540479897@infradead.org>

  "Look ma, no branches!"

Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 kernel/events/internal.h |   17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -205,16 +205,15 @@ DEFINE_OUTPUT_COPY(__output_copy_user, a
 
 static inline int get_recursion_context(int *recursion)
 {
-	int rctx;
+	unsigned int pc = preempt_count();
+	unsigned int rctx = 0;
 
-	if (unlikely(in_nmi()))
-		rctx = 3;
-	else if (in_irq())
-		rctx = 2;
-	else if (in_serving_softirq())
-		rctx = 1;
-	else
-		rctx = 0;
+	if (pc & (NMI_MASK))
+		rctx++;
+	if (pc & (NMI_MASK | HARDIRQ_MASK))
+		rctx++;
+	if (pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET))
+		rctx++;
 
 	if (recursion[rctx])
 		return -1;



  parent reply index

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-30 15:13 [PATCH 0/6] perf: Reduce stack usage (and misc bits) Peter Zijlstra
2020-10-30 15:13 ` [PATCH 1/6] perf: Reduce stack usage of perf_output_begin() Peter Zijlstra
2020-11-10 12:45   ` [tip: perf/urgent] " tip-bot2 for Peter Zijlstra
2020-10-30 15:13 ` [PATCH 2/6] perf/x86: Reduce stack usage for x86_pmu::drain_pebs() Peter Zijlstra
2020-11-10 12:45   ` [tip: perf/urgent] " tip-bot2 for Peter Zijlstra
2020-10-30 15:13 ` [PATCH 3/6] perf: Fix get_recursion_context() Peter Zijlstra
2020-11-10 12:45   ` [tip: perf/urgent] " tip-bot2 for Peter Zijlstra
2020-10-30 15:13 ` Peter Zijlstra [this message]
2020-10-30 17:11   ` [PATCH 4/6] perf: Optimize get_recursion_context() Jesper Dangaard Brouer
2020-10-30 20:22     ` Steven Rostedt
2020-10-30 22:14       ` Thomas Gleixner
2020-10-30 23:31         ` Steven Rostedt
2020-10-31 11:23           ` Peter Zijlstra
2020-10-30 23:01       ` Peter Zijlstra
2020-10-31 12:11         ` David Laight
2020-10-31 13:18           ` David Laight
2020-11-09 12:12           ` Peter Zijlstra
2020-11-09 14:14             ` David Laight
2020-11-10 12:45   ` [tip: perf/urgent] " tip-bot2 for Peter Zijlstra
2020-10-30 15:13 ` [PATCH 5/6] perf/arch: Remove perf_sample_data::regs_user_copy Peter Zijlstra
2020-11-10 12:45   ` [tip: perf/urgent] " tip-bot2 for Peter Zijlstra
2020-10-30 15:13 ` [PATCH 6/6] perf/x86: Make dummy_iregs static Peter Zijlstra
2020-11-10 12:45   ` [tip: perf/urgent] " tip-bot2 for Peter Zijlstra

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