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Message-Id: <20190816021343.27160-1-yao.jin@linux.intel.com>
Date:   Fri, 16 Aug 2019 10:13:43 +0800
From:   Jin Yao <yao.jin@...ux.intel.com>
To:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com
Cc:     Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com,
        Jin Yao <yao.jin@...ux.intel.com>
Subject: [PATCH v5] perf diff: Report noisy for cycles diff

This patch prints the stddev and hist for the cycles diff of
program block. It can help us to understand if the cycles
is noisy or not.

This patch is inspired by Andi Kleen's patch
https://lwn.net/Articles/600471/

We create new option '--cycles-hist'.

Example:

perf record -b ./div
perf record -b ./div
perf diff -c cycles

  # Baseline                                       [Program Block Range] Cycles Diff  Shared Object      Symbol
  # ........  ......................................................................  .................  ............................
  #
      46.72%                                             [div.c:40 -> div.c:40]    0  div                [.] main
      46.72%                                             [div.c:42 -> div.c:44]    0  div                [.] main
      46.72%                                             [div.c:42 -> div.c:39]    0  div                [.] main
      20.54%                                 [random_r.c:357 -> random_r.c:394]    1  libc-2.27.so       [.] __random_r
      20.54%                                 [random_r.c:357 -> random_r.c:380]    0  libc-2.27.so       [.] __random_r
      20.54%                                 [random_r.c:388 -> random_r.c:388]    0  libc-2.27.so       [.] __random_r
      20.54%                                 [random_r.c:388 -> random_r.c:391]    0  libc-2.27.so       [.] __random_r
      17.04%                                     [random.c:288 -> random.c:291]    0  libc-2.27.so       [.] __random
      17.04%                                     [random.c:291 -> random.c:291]    0  libc-2.27.so       [.] __random
      17.04%                                     [random.c:293 -> random.c:293]    0  libc-2.27.so       [.] __random
      17.04%                                     [random.c:295 -> random.c:295]    0  libc-2.27.so       [.] __random
      17.04%                                     [random.c:295 -> random.c:295]    0  libc-2.27.so       [.] __random
      17.04%                                     [random.c:298 -> random.c:298]    0  libc-2.27.so       [.] __random
       8.40%                                             [div.c:22 -> div.c:25]    0  div                [.] compute_flag
       8.40%                                             [div.c:27 -> div.c:28]    0  div                [.] compute_flag
       5.14%                                           [rand.c:26 -> rand.c:27]    0  libc-2.27.so       [.] rand
       5.14%                                           [rand.c:28 -> rand.c:28]    0  libc-2.27.so       [.] rand
       2.15%                                         [rand@...+0 -> rand@...+0]    0  div                [.] rand@plt
       0.00%                                                                          [kernel.kallsyms]  [k] __x86_indirect_thunk_rax
       0.00%                                       [do_mmap+714 -> do_mmap+732]  -10  [kernel.kallsyms]  [k] do_mmap
       0.00%                                       [do_mmap+737 -> do_mmap+765]    1  [kernel.kallsyms]  [k] do_mmap
       0.00%                                       [do_mmap+262 -> do_mmap+299]    0  [kernel.kallsyms]  [k] do_mmap
       0.00%         [__x86_indirect_thunk_r15+0 -> __x86_indirect_thunk_r15+0]    7  [kernel.kallsyms]  [k] __x86_indirect_thunk_r15
       0.00%                   [native_sched_clock+0 -> native_sched_clock+119]   -1  [kernel.kallsyms]  [k] native_sched_clock
       0.00%                        [native_write_msr+0 -> native_write_msr+16]  -13  [kernel.kallsyms]  [k] native_write_msr

When we enable the option '--cycles-hist', the output is

perf diff -c cycles --cycles-hist

  # Baseline                                       [Program Block Range] Cycles Diff        stddev/Hist  Shared Object      Symbol
  # ........  ......................................................................  .................  .................  ............................
  #
      46.72%                                             [div.c:40 -> div.c:40]    0  ± 37.8% ▁█▁▁██▁█   div                [.] main
      46.72%                                             [div.c:42 -> div.c:44]    0  ± 49.4% ▁▁▂█▂▂▂▂   div                [.] main
      46.72%                                             [div.c:42 -> div.c:39]    0  ± 24.1% ▃█▂▄▁▃▂▁   div                [.] main
      20.54%                                 [random_r.c:357 -> random_r.c:394]    1  ± 33.5% ▅▂▁█▃▁▂▁   libc-2.27.so       [.] __random_r
      20.54%                                 [random_r.c:357 -> random_r.c:380]    0  ± 39.4% ▁▁█▁██▅▁   libc-2.27.so       [.] __random_r
      20.54%                                 [random_r.c:388 -> random_r.c:388]    0                     libc-2.27.so       [.] __random_r
      20.54%                                 [random_r.c:388 -> random_r.c:391]    0  ± 41.2% ▁▃▁▂█▄▃▁   libc-2.27.so       [.] __random_r
      17.04%                                     [random.c:288 -> random.c:291]    0  ± 48.8% ▁▁▁▁███▁   libc-2.27.so       [.] __random
      17.04%                                     [random.c:291 -> random.c:291]    0  ±100.0% ▁█▁▁▁▁▁▁   libc-2.27.so       [.] __random
      17.04%                                     [random.c:293 -> random.c:293]    0  ±100.0% ▁█▁▁▁▁▁▁   libc-2.27.so       [.] __random
      17.04%                                     [random.c:295 -> random.c:295]    0  ±100.0% ▁█▁▁▁▁▁▁   libc-2.27.so       [.] __random
      17.04%                                     [random.c:295 -> random.c:295]    0                     libc-2.27.so       [.] __random
      17.04%                                     [random.c:298 -> random.c:298]    0  ± 75.6% ▃█▁▁▁▁▁▁   libc-2.27.so       [.] __random
       8.40%                                             [div.c:22 -> div.c:25]    0  ± 42.1% ▁▃▁▁███▁   div                [.] compute_flag
       8.40%                                             [div.c:27 -> div.c:28]    0  ± 41.8% ██▁▁▄▁▁▄   div                [.] compute_flag
       5.14%                                           [rand.c:26 -> rand.c:27]    0  ± 37.8% ▁▁▁████▁   libc-2.27.so       [.] rand
       5.14%                                           [rand.c:28 -> rand.c:28]    0                     libc-2.27.so       [.] rand
       2.15%                                         [rand@...+0 -> rand@...+0]    0                     div                [.] rand@plt
       0.00%                                                                                             [kernel.kallsyms]  [k] __x86_indirect_thunk_rax
       0.00%                                       [do_mmap+714 -> do_mmap+732]  -10                     [kernel.kallsyms]  [k] do_mmap
       0.00%                                       [do_mmap+737 -> do_mmap+765]    1                     [kernel.kallsyms]  [k] do_mmap
       0.00%                                       [do_mmap+262 -> do_mmap+299]    0                     [kernel.kallsyms]  [k] do_mmap
       0.00%         [__x86_indirect_thunk_r15+0 -> __x86_indirect_thunk_r15+0]    7                     [kernel.kallsyms]  [k] __x86_indirect_thunk_r15
       0.00%                   [native_sched_clock+0 -> native_sched_clock+119]   -1  ± 38.5% ▄█▁        [kernel.kallsyms]  [k] native_sched_clock
       0.00%                        [native_write_msr+0 -> native_write_msr+16]  -13  ± 47.1% ▁█▇▃▁▁     [kernel.kallsyms]  [k] native_write_msr

 v5:
 ---
 1. Refine the use of data__hpp_register() in ui_init() according to
    Jiri's suggestion.

 v4:
 ---
 1. Rename the new option from '--noisy' to '--cycles-hist'
 2. Remove the option '-n'.
 3. Only update the spark value and stats when '--cycles-hist' is enabled.
 4. Remove the code of printing '..'.

 v3:
 ---
 1. Move the histogram to a separate column
 2. Move the svals[] out of struct stats

 v2:
 ---
 Jiri got a compile error,

  CC       builtin-diff.o
  builtin-diff.c: In function ‘compute_cycles_diff’:
  builtin-diff.c:712:10: error: taking the absolute value of unsigned type ‘u64’ {aka ‘long unsigned int’} has no effect [-Werror=absolute-value]
  712 |          labs(pair->block_info->cycles_spark[i] -
      |          ^~~~

 Because the result of u64 - u64 is still u64. Now we change the type of
 cycles_spark[] to s64.

Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
---
 tools/perf/Documentation/perf-diff.txt |   5 +
 tools/perf/builtin-diff.c              | 148 ++++++++++++++++++++++++-
 tools/perf/util/Build                  |   1 +
 tools/perf/util/annotate.c             |   4 +
 tools/perf/util/annotate.h             |   2 +
 tools/perf/util/sort.h                 |   4 +
 tools/perf/util/spark.c                |  34 ++++++
 tools/perf/util/spark.h                |   8 ++
 tools/perf/util/symbol.h               |   2 +
 9 files changed, 206 insertions(+), 2 deletions(-)
 create mode 100644 tools/perf/util/spark.c
 create mode 100644 tools/perf/util/spark.h

diff --git a/tools/perf/Documentation/perf-diff.txt b/tools/perf/Documentation/perf-diff.txt
index d5cc15e651cf..f50ca0fef0a4 100644
--- a/tools/perf/Documentation/perf-diff.txt
+++ b/tools/perf/Documentation/perf-diff.txt
@@ -95,6 +95,11 @@ OPTIONS
         diff.compute config option.  See COMPARISON METHODS section for
         more info.
 
+--cycles-hist::
+	Report a histogram and the standard deviation for cycles data.
+	It can help us to judge if the reported cycles data is noisy or
+	not. This option should be used with '-c cycles'.
+
 -p::
 --period::
         Show period values for both compared hist entries.
diff --git a/tools/perf/builtin-diff.c b/tools/perf/builtin-diff.c
index e91c0d798181..febfe8ed4ccd 100644
--- a/tools/perf/builtin-diff.c
+++ b/tools/perf/builtin-diff.c
@@ -21,6 +21,7 @@
 #include "util/time-utils.h"
 #include "util/annotate.h"
 #include "util/map.h"
+#include "util/spark.h"
 #include <linux/zalloc.h>
 
 #include <errno.h>
@@ -48,6 +49,7 @@ enum {
 	PERF_HPP_DIFF__FORMULA,
 	PERF_HPP_DIFF__DELTA_ABS,
 	PERF_HPP_DIFF__CYCLES,
+	PERF_HPP_DIFF__CYCLES_HIST,
 
 	PERF_HPP_DIFF__MAX_INDEX
 };
@@ -82,6 +84,7 @@ static bool force;
 static bool show_period;
 static bool show_formula;
 static bool show_baseline_only;
+static bool cycles_hist;
 static unsigned int sort_compute = 1;
 
 static s64 compute_wdiff_w1;
@@ -159,6 +162,10 @@ static struct header_column {
 	[PERF_HPP_DIFF__CYCLES] = {
 		.name  = "[Program Block Range] Cycles Diff",
 		.width = 70,
+	},
+	[PERF_HPP_DIFF__CYCLES_HIST] = {
+		.name  = "stddev/Hist",
+		.width = NUM_SPARKS + 9,
 	}
 };
 
@@ -605,6 +612,9 @@ static void init_block_info(struct block_info *bi, struct symbol *sym,
 	bi->cycles_aggr = ch->cycles_aggr;
 	bi->num = ch->num;
 	bi->num_aggr = ch->num_aggr;
+
+	memcpy(bi->cycles_spark, ch->cycles_spark,
+	       NUM_SPARKS * sizeof(u64));
 }
 
 static int process_block_per_sym(struct hist_entry *he)
@@ -684,6 +694,21 @@ static struct hist_entry *get_block_pair(struct hist_entry *he,
 	return NULL;
 }
 
+static void init_spark_values(unsigned long *svals, int num)
+{
+	for (int i = 0; i < num; i++)
+		svals[i] = 0;
+}
+
+static void update_spark_value(unsigned long *svals, int num,
+			       struct stats *stats, u64 val)
+{
+	int n = stats->n;
+
+	if (n < num)
+		svals[n] = val;
+}
+
 static void compute_cycles_diff(struct hist_entry *he,
 				struct hist_entry *pair)
 {
@@ -692,6 +717,26 @@ static void compute_cycles_diff(struct hist_entry *he,
 		pair->diff.cycles =
 			pair->block_info->cycles_aggr / pair->block_info->num_aggr -
 			he->block_info->cycles_aggr / he->block_info->num_aggr;
+
+		if (!cycles_hist)
+			return;
+
+		init_stats(&pair->diff.stats);
+		init_spark_values(pair->diff.svals, NUM_SPARKS);
+
+		for (int i = 0; i < pair->block_info->num; i++) {
+			u64 val;
+
+			if (i >= he->block_info->num || i >= NUM_SPARKS)
+				break;
+
+			val = labs(pair->block_info->cycles_spark[i] -
+				     he->block_info->cycles_spark[i]);
+
+			update_spark_value(pair->diff.svals, NUM_SPARKS,
+					   &pair->diff.stats, val);
+			update_stats(&pair->diff.stats, val);
+		}
 	}
 }
 
@@ -1250,6 +1295,9 @@ static const struct option options[] = {
 		    "Show period values."),
 	OPT_BOOLEAN('F', "formula", &show_formula,
 		    "Show formula."),
+	OPT_BOOLEAN(0, "cycles-hist", &cycles_hist,
+		    "Show cycles histogram and standard deviation "
+		    "- WARNING: use only with -c cycles."),
 	OPT_BOOLEAN('D', "dump-raw-trace", &dump_trace,
 		    "dump raw trace in ASCII"),
 	OPT_BOOLEAN('f', "force", &force, "don't complain, do it"),
@@ -1457,6 +1505,90 @@ static int hpp__color_cycles(struct perf_hpp_fmt *fmt,
 	return __hpp__color_compare(fmt, hpp, he, COMPUTE_CYCLES);
 }
 
+static int all_zero(unsigned long *vals, int len)
+{
+	int i;
+
+	for (i = 0; i < len; i++)
+		if (vals[i] != 0)
+			return 0;
+	return 1;
+}
+
+static int print_cycles_spark(char *bf, int size, unsigned long *svals, u64 n)
+{
+	int printed;
+
+	if (n <= 1)
+		return 0;
+
+	if (n > NUM_SPARKS)
+		n = NUM_SPARKS;
+	if (all_zero(svals, n))
+		return 0;
+
+	printed = print_spark(bf, size, svals, n);
+	printed += scnprintf(bf + printed, size - printed, " ");
+	return printed;
+}
+
+static int hpp__color_cycles_hist(struct perf_hpp_fmt *fmt,
+			    struct perf_hpp *hpp, struct hist_entry *he)
+{
+	struct diff_hpp_fmt *dfmt =
+		container_of(fmt, struct diff_hpp_fmt, fmt);
+	struct hist_entry *pair = get_pair_fmt(he, dfmt);
+	struct block_hist *bh = container_of(he, struct block_hist, he);
+	struct block_hist *bh_pair;
+	struct hist_entry *block_he;
+	char spark[32], buf[128];
+	double r;
+	int ret, pad;
+
+	if (!pair) {
+		if (bh->block_idx)
+			hpp->skip = true;
+
+		goto no_print;
+	}
+
+	bh_pair = container_of(pair, struct block_hist, he);
+
+	block_he = hists__get_entry(&bh_pair->block_hists, bh->block_idx);
+	if (!block_he) {
+		hpp->skip = true;
+		goto no_print;
+	}
+
+	ret = print_cycles_spark(spark, sizeof(spark), block_he->diff.svals,
+				 block_he->diff.stats.n);
+
+	r = rel_stddev_stats(stddev_stats(&block_he->diff.stats),
+			     avg_stats(&block_he->diff.stats));
+
+	if (ret) {
+		/*
+		 * Padding spaces if number of sparks less than NUM_SPARKS
+		 * otherwise the output is not aligned.
+		 */
+		pad = NUM_SPARKS - ((ret - 1) / 3);
+		scnprintf(buf, sizeof(buf), "%s%5.1f%% %s", "\u00B1", r, spark);
+		ret = scnprintf(hpp->buf, hpp->size, "%*s",
+				dfmt->header_width, buf);
+
+		if (pad) {
+			ret += scnprintf(hpp->buf + ret, hpp->size - ret,
+					 "%-*s", pad, " ");
+		}
+
+		return ret;
+	}
+
+no_print:
+	return scnprintf(hpp->buf, hpp->size, "%*s",
+			dfmt->header_width, " ");
+}
+
 static void
 hpp__entry_unpair(struct hist_entry *he, int idx, char *buf, size_t size)
 {
@@ -1662,6 +1794,10 @@ static void data__hpp_register(struct data__file *d, int idx)
 		fmt->color = hpp__color_cycles;
 		fmt->sort  = hist_entry__cmp_nop;
 		break;
+	case PERF_HPP_DIFF__CYCLES_HIST:
+		fmt->color = hpp__color_cycles_hist;
+		fmt->sort  = hist_entry__cmp_nop;
+		break;
 	default:
 		fmt->sort  = hist_entry__cmp_nop;
 		break;
@@ -1688,8 +1824,13 @@ static int ui_init(void)
 		 *   PERF_HPP_DIFF__RATIO
 		 *   PERF_HPP_DIFF__WEIGHTED_DIFF
 		 */
-		data__hpp_register(d, i ? compute_2_hpp[compute] :
-					  PERF_HPP_DIFF__BASELINE);
+		if (cycles_hist && i && (compute == COMPUTE_CYCLES)) {
+			data__hpp_register(d, PERF_HPP_DIFF__CYCLES);
+			data__hpp_register(d, PERF_HPP_DIFF__CYCLES_HIST);
+		} else {
+			data__hpp_register(d, i ? compute_2_hpp[compute] :
+						  PERF_HPP_DIFF__BASELINE);
+		}
 
 		/*
 		 * And the rest:
@@ -1845,6 +1986,9 @@ int cmd_diff(int argc, const char **argv)
 	if (quiet)
 		perf_quiet_option();
 
+	if (cycles_hist && (compute != COMPUTE_CYCLES))
+		usage_with_options(diff_usage, options);
+
 	symbol__annotation_init();
 
 	if (symbol__init(NULL) < 0)
diff --git a/tools/perf/util/Build b/tools/perf/util/Build
index 7cda749059a9..2e3ed877a703 100644
--- a/tools/perf/util/Build
+++ b/tools/perf/util/Build
@@ -89,6 +89,7 @@ perf-y += cloexec.o
 perf-y += call-path.o
 perf-y += rwsem.o
 perf-y += thread-stack.o
+perf-y += spark.o
 perf-$(CONFIG_AUXTRACE) += auxtrace.o
 perf-$(CONFIG_AUXTRACE) += intel-pt-decoder/
 perf-$(CONFIG_AUXTRACE) += intel-pt.o
diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
index e0518dc4c4d2..a43354dbc836 100644
--- a/tools/perf/util/annotate.c
+++ b/tools/perf/util/annotate.c
@@ -847,6 +847,10 @@ static int __symbol__account_cycles(struct cyc_hist *ch,
 			   ch[offset].start < start)
 			return 0;
 	}
+
+	if (ch[offset].num < NUM_SPARKS)
+		ch[offset].cycles_spark[ch[offset].num] = cycles;
+
 	ch[offset].have_start = have_start;
 	ch[offset].start = start;
 	ch[offset].cycles += cycles;
diff --git a/tools/perf/util/annotate.h b/tools/perf/util/annotate.h
index d94be9140e31..7776ff4480af 100644
--- a/tools/perf/util/annotate.h
+++ b/tools/perf/util/annotate.h
@@ -11,6 +11,7 @@
 #include <pthread.h>
 #include <asm/bug.h>
 #include "symbol_conf.h"
+#include "spark.h"
 
 struct hist_browser_timer;
 struct hist_entry;
@@ -235,6 +236,7 @@ struct cyc_hist {
 	u64	cycles_aggr;
 	u64	cycles_max;
 	u64	cycles_min;
+	s64	cycles_spark[NUM_SPARKS];
 	u32	num;
 	u32	num_aggr;
 	u8	have_start;
diff --git a/tools/perf/util/sort.h b/tools/perf/util/sort.h
index 5e34676a98e8..14061e42a862 100644
--- a/tools/perf/util/sort.h
+++ b/tools/perf/util/sort.h
@@ -23,6 +23,8 @@
 #include "parse-events.h"
 #include "hist.h"
 #include "srcline.h"
+#include "stat.h"
+#include "spark.h"
 
 struct thread;
 
@@ -83,6 +85,8 @@ struct hist_entry_diff {
 		/* PERF_HPP_DIFF__CYCLES */
 		s64	cycles;
 	};
+	struct stats	stats;
+	unsigned long	svals[NUM_SPARKS];
 };
 
 struct hist_entry_ops {
diff --git a/tools/perf/util/spark.c b/tools/perf/util/spark.c
new file mode 100644
index 000000000000..70272a8b81a6
--- /dev/null
+++ b/tools/perf/util/spark.c
@@ -0,0 +1,34 @@
+#include <stdio.h>
+#include <limits.h>
+#include <string.h>
+#include <stdlib.h>
+#include "spark.h"
+#include "stat.h"
+
+#define SPARK_SHIFT 8
+
+/* Print spark lines on outf for numval values in val. */
+int print_spark(char *bf, int size, unsigned long *val, int numval)
+{
+	static const char *ticks[NUM_SPARKS] = {
+		"▁",  "▂", "▃", "▄", "▅", "▆", "▇", "█"
+	};
+	int i, printed = 0;
+	unsigned long min = ULONG_MAX, max = 0, f;
+
+	for (i = 0; i < numval; i++) {
+		if (val[i] < min)
+			min = val[i];
+		if (val[i] > max)
+			max = val[i];
+	}
+	f = ((max - min) << SPARK_SHIFT) / (NUM_SPARKS - 1);
+	if (f < 1)
+		f = 1;
+	for (i = 0; i < numval; i++) {
+		printed += scnprintf(bf + printed, size - printed, "%s",
+				     ticks[((val[i] - min) << SPARK_SHIFT) / f]);
+	}
+
+	return printed;
+}
diff --git a/tools/perf/util/spark.h b/tools/perf/util/spark.h
new file mode 100644
index 000000000000..25402d7d7a64
--- /dev/null
+++ b/tools/perf/util/spark.h
@@ -0,0 +1,8 @@
+#ifndef SPARK_H
+#define SPARK_H 1
+
+#define NUM_SPARKS 8
+
+int print_spark(char *bf, int size, unsigned long *val, int numval);
+
+#endif
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index 183f630cb5f1..499917165394 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -12,6 +12,7 @@
 #include "branch.h"
 #include "path.h"
 #include "symbol_conf.h"
+#include "spark.h"
 
 #ifdef HAVE_LIBELF_SUPPORT
 #include <libelf.h>
@@ -137,6 +138,7 @@ struct block_info {
 	u64			end;
 	u64			cycles;
 	u64			cycles_aggr;
+	s64			cycles_spark[NUM_SPARKS];
 	int			num;
 	int			num_aggr;
 	refcount_t		refcnt;
-- 
2.17.1

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