linux-kernel - [PATCH v5 1/4] perf/core,x86: introduce swap_task

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Date:   Fri, 25 Oct 2019 11:58:08 +0300
From:   Alexey Budankov <alexey.budankov@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Stephane Eranian <eranian@...gle.com>,
        Ian Rogers <irogers@...gle.com>,
        Song Liu <songliubraving@...com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH v5 1/4] perf/core,x86: introduce swap_task_ctx() method at
 struct pmu


Declare swap_task_ctx() methods at the generic and x86 specific
pmu types to bridge calls to platform specific pmu code on optimized
context switch path between equivalent task perf event contexts.

Signed-off-by: Alexey Budankov <alexey.budankov@...ux.intel.com>
---
 arch/x86/events/perf_event.h | 8 ++++++++
 include/linux/perf_event.h   | 9 +++++++++
 2 files changed, 17 insertions(+)

diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index ecacfbf4ebc1..5384317eaa16 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -682,6 +682,14 @@ struct x86_pmu {
 	 */
 	atomic_t	lbr_exclusive[x86_lbr_exclusive_max];
 
+	/*
+	 * perf task context (i.e. struct perf_event_context::task_ctx_data)
+	 * switch helper to bridge calls from perf/core to perf/x86.
+	 * See struct pmu::swap_task_ctx() usage for examples;
+	 */
+	void		(*swap_task_ctx)(struct perf_event_context *prev,
+					 struct perf_event_context *next);
+
 	/*
 	 * AMD bits
 	 */
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 587ae4d002f5..7887e4a3d487 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -410,6 +410,15 @@ struct pmu {
 	 */
 	size_t				task_ctx_size;
 
+	/*
+	 * PMU specific parts of task perf event context (i.e. ctx->task_ctx_data)
+	 * can be synchronized using this function. See Intel LBR callstack support
+	 * implementation and Perf core context switch handling callbacks for usage
+	 * examples.
+	 */
+	void (*swap_task_ctx)		(struct perf_event_context *prev,
+					 struct perf_event_context *next);
+					/* optional */
 
 	/*
 	 * Set up pmu-private data structures for an AUX area
-- 
2.20.1