linux-kernel - [PATCH] perf: Change the layout of perf_sample

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Date:   Thu, 22 Sep 2022 13:55:50 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Song Liu <songliubraving@...com>,
        Ravi Bangoria <ravi.bangoria@....com>,
        Stephane Eranian <eranian@...gle.com>,
        Kan Liang <kan.liang@...ux.intel.com>
Subject: [PATCH] perf: Change the layout of perf_sample_data

With recent change, it can set fields only if it's actually used.
Change the data layout so that it can have commonly used fields together
in a cache line boundary.  The main user (the perf tools) sets the
IP, TID, TIME, PERIOD always.  Also group relevant fields like addr,
phys_addr and data_page_size.

Suggested-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 include/linux/perf_event.h | 35 +++++++++++++++++------------------
 1 file changed, 17 insertions(+), 18 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index e9b151cde491..8c16dae6e6bb 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1023,25 +1023,13 @@ extern u64 perf_event_read_value(struct perf_event *event,
 
 
 struct perf_sample_data {
-	/*
-	 * Fields set by perf_sample_data_init(), group so as to
-	 * minimize the cachelines touched.
-	 */
 	u64				sample_flags;
 	u64				period;
-
+	u64				type;
 	/*
-	 * The other fields, optionally {set,used} by
-	 * perf_{prepare,output}_sample().
+	 * Fields set commonly by perf tools, group so as to
+	 * minimize the cachelines touched.
 	 */
-	struct perf_branch_stack	*br_stack;
-	union perf_sample_weight	weight;
-	union  perf_mem_data_src	data_src;
-	u64				txn;
-	u64				addr;
-	struct perf_raw_record		*raw;
-
-	u64				type;
 	u64				ip;
 	struct {
 		u32	pid;
@@ -1049,22 +1037,33 @@ struct perf_sample_data {
 	}				tid_entry;
 	u64				time;
 	u64				id;
-	u64				stream_id;
 	struct {
 		u32	cpu;
 		u32	reserved;
 	}				cpu_entry;
+
+	/*
+	 * The other fields, optionally {set,used} by
+	 * perf_{prepare,output}_sample().
+	 */
 	struct perf_callchain_entry	*callchain;
-	u64				aux_size;
+	struct perf_raw_record		*raw;
+	struct perf_branch_stack	*br_stack;
+	union perf_sample_weight	weight;
+	union  perf_mem_data_src	data_src;
+	u64				txn;
 
 	struct perf_regs		regs_user;
 	struct perf_regs		regs_intr;
 	u64				stack_user_size;
 
-	u64				phys_addr;
+	u64				stream_id;
 	u64				cgroup;
+	u64				addr;
+	u64				phys_addr;
 	u64				data_page_size;
 	u64				code_page_size;
+	u64				aux_size;
 } ____cacheline_aligned;
 
 /* default value for data source */
-- 
2.37.3.998.g577e59143f-goog