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Date: Tue, 10 Jun 2014 07:04:43 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Jiri Olsa <jolsa@...nel.org>
Cc: linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
Arnaldo Carvalho de Melo <acme@...radead.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 15/15] perf tools: Support spark lines in perf stat
* Jiri Olsa <jolsa@...nel.org> wrote:
> From: Andi Kleen <ak@...ux.intel.com>
>
> perf stat -rX prints the stddev for multiple measurements.
Call it "--repeat X", that's how most people know it.
> Just looking at the stddev for judging the quality of the data
> is a bit dangerous The simplest sanity check is to just look
"Dangerous?". Unexplained FUD. Also a missing perid.
> at a simple plot. This patchs add a sparkline to the end
> of the measurements to make it simple to judge the data.
Should explain what a 'sparkline' is when it's first mentioned, not 2
sentences later.
> The sparkline only uses UTF-8, so should be readable
> in all modern tools and terminals.
>
> The sparkline is between the minimum and maximum of the data,
> so it's mainly a indicator of variance. To keep the code
> simple and make the output not too wide only the first
> 8 values are printed. If more values are there it adds '..'
>
> The code is inspired by Zach Holman's spark shell script.
Zach Holman should be on Cc:.
> Example output (view in non-proportial font):
>
> Performance counter stats for 'true' (10 runs):
>
> 0.175672 task-clock (msec) # 0.555 CPUs utilized ( +- 1.77% ) █▄▁▁▁▁▁▁..
> 0 context-switches # 0.000 K/sec
> 0 cpu-migrations # 0.000 K/sec
> 114 page-faults # 0.647 M/sec ( +- 0.14% ) ▁█▁▁████..
> 520,798 cycles # 2.965 GHz ( +- 1.75% ) █▄▁▁▁▁▁▁..
> 433,525 instructions # 0.83 insns per cycle ( +- 0.28% ) ▅▇▅▄▇█▁▆..
> 83,012 branches # 472.537 M/sec ( +- 0.31% ) ▅▇▆▄▇█▁▆..
> 3,157 branch-misses # 3.80% of all branches ( +- 2.55% ) ▇█▃▅▁▃▁▂..
>
> 0.000316660 seconds time elapsed ( +- 1.78% ) █▅▁▁▁▁▁▁..
The noise data is not aligned vertically in the changelog - is it in
the real code? It should be.
> As you can see even in the most simple run there are quite
> interesting patterns. The time sparkline suggests it would be also
> useful to have an option to throw the first measurement away.
First two should be thrown away, probably, to reduce the resulting
stddev.
> Known issues:
> - Makes the perf stat output wider. Could be adjust by shrinking
> some white space. Not done so far.
> - No output for -A/--per-socket/--per-core with -rX. This code
> is missing the basic noise detection code. Once it's added there
> sparklines could be shown too.
The feauture looks useful, but at minimum the second shortcoming
should be fixed first in a separate patch, before applying new
features and further complicating the code.
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> Link: http://lkml.kernel.org/r/1401838086-17750-1-git-send-email-andi@firstfloor.org
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---
> tools/perf/Documentation/perf-stat.txt | 4 ++++
> tools/perf/Makefile.perf | 1 +
> tools/perf/builtin-stat.c | 12 ++++++++++++
> tools/perf/util/spark.c | 31 +++++++++++++++++++++++++++++++
> tools/perf/util/spark.h | 4 ++++
> tools/perf/util/stat.c | 34 ++++++++++++++++++++++++++++++++++
> tools/perf/util/stat.h | 10 ++++++++++
> 7 files changed, 96 insertions(+)
> create mode 100644 tools/perf/util/spark.c
> create mode 100644 tools/perf/util/spark.h
>
> diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
> index 29ee857..840c1db 100644
> --- a/tools/perf/Documentation/perf-stat.txt
> +++ b/tools/perf/Documentation/perf-stat.txt
> @@ -53,6 +53,10 @@ OPTIONS
> -r::
> --repeat=<n>::
> repeat command and print average + stddev (max: 100). 0 means forever.
> + In addition it prints a spark line (when not in CSV mode), which visualizes the
> + variance between minimum and maximum of the measurements. This allows a simple sanity
> + check of the measurements. Only 8 values are printed, when more are available
> + it adds ..
>
> -B::
> --big-num::
> diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> index 9670a16..90b3aa7 100644
> --- a/tools/perf/Makefile.perf
> +++ b/tools/perf/Makefile.perf
> @@ -359,6 +359,7 @@ LIB_OBJS += $(OUTPUT)util/trace-event-scripting.o
> LIB_OBJS += $(OUTPUT)util/trace-event.o
> LIB_OBJS += $(OUTPUT)util/svghelper.o
> LIB_OBJS += $(OUTPUT)util/sort.o
> +LIB_OBJS += $(OUTPUT)util/spark.o
> LIB_OBJS += $(OUTPUT)util/hist.o
> LIB_OBJS += $(OUTPUT)util/probe-event.o
> LIB_OBJS += $(OUTPUT)util/util.o
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index 65a151e..cb0f7c5 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -1176,6 +1176,9 @@ static void print_aggr(char *prefix)
> if (run != ena)
> fprintf(output, " (%.2f%%)",
> 100.0 * run / ena);
> +
> + fputc(' ', output);
> + print_stat_spark(output, counter->priv);
> }
> fputc('\n', output);
> }
> @@ -1229,6 +1232,9 @@ static void print_counter_aggr(struct perf_evsel *counter, char *prefix)
> return;
> }
>
> + fputc(' ', output);
> + print_stat_spark(output, counter->priv);
> +
> if (scaled) {
> double avg_enabled, avg_running;
>
> @@ -1295,6 +1301,9 @@ static void print_counter(struct perf_evsel *counter, char *prefix)
> if (run != ena)
> fprintf(output, " (%.2f%%)",
> 100.0 * run / ena);
> +
> + fputc(' ', output);
> + print_stat_spark(output, counter->priv);
> }
> fputc('\n', output);
> }
> @@ -1355,6 +1364,9 @@ static void print_stat(int argc, const char **argv)
> fprintf(output, " ");
> print_noise_pct(stddev_stats(&walltime_nsecs_stats),
> avg_stats(&walltime_nsecs_stats));
> +
> + fputc(' ', output);
> + print_stat_spark(output, &walltime_nsecs_stats);
Why is that 2-line pattern repeated 4 times?
> }
> fprintf(output, "\n\n");
> }
> diff --git a/tools/perf/util/spark.c b/tools/perf/util/spark.c
> new file mode 100644
> index 0000000..5a1033f
> --- /dev/null
> +++ b/tools/perf/util/spark.c
> @@ -0,0 +1,31 @@
> +#include <stdio.h>
> +#include <limits.h>
> +#include "spark.h"
> +
> +#define NUM_SPARKS 8
> +#define SPARK_SHIFT 8
> +
> +/* Print spark lines on outf for numval values in val. */
> +void print_spark(FILE *outf, unsigned long long *val, int numval)
The output file is called 'output' in the calling context, there's no
reason to randomly depart from that convention and introduce a random
new one: not a single existing line in tools/perf/ calls an output
file 'outf'.
Also, I don't see 'numval' used anywhere in perf. The canonical naming
would be different.
> +{
> + static const char *ticks[NUM_SPARKS] = {
> + "▁", "▂", "▃", "▄", "▅", "▆", "▇", "█"
> + };
> + int i;
> + unsigned long long min = ULLONG_MAX, max = 0, f;
min/max is a somewhat sloppy name as well (easy to confuse with
min()/max()), should be somehing like min_val/max_val, which is in
line .
> +
> + 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++) {
> + int index = ((val[i] - min) << SPARK_SHIFT) / f;
> + if (index >= 0 && index < NUM_SPARKS)
> + fputs(ticks[index], outf);
That's not primarily an 'index', it's an indexed 'variance' value. So
'variance_idx' or so.
> + }
> +}
> diff --git a/tools/perf/util/spark.h b/tools/perf/util/spark.h
> new file mode 100644
> index 0000000..d9ebc94
> --- /dev/null
> +++ b/tools/perf/util/spark.h
> @@ -0,0 +1,4 @@
> +#ifndef SPARK_H
> +#define SPARK_H 1
> +void print_spark(FILE *outf, unsigned long long *val, int numval);
> +#endif
> diff --git a/tools/perf/util/stat.c b/tools/perf/util/stat.c
> index 6506b3d..a7c02c5 100644
> --- a/tools/perf/util/stat.c
> +++ b/tools/perf/util/stat.c
> @@ -1,10 +1,16 @@
> #include <math.h>
> +#include <stdio.h>
>
> #include "stat.h"
> +#include "spark.h"
>
> void update_stats(struct stats *stats, u64 val)
> {
> double delta;
> + int n = stats->n;
> +
> + if (n < NUM_SPARK_VALS)
> + stats->svals[n] = val;
>
> stats->n++;
> delta = val - stats->mean;
> stats->mean += delta / stats->n;
It is absolutely sloppy, potentially misleading and unrobust to put an
integer rounded value of 'double n' into a local variable named 'int
n' ...
> @@ -61,3 +67,31 @@ double rel_stddev_stats(double stddev, double avg)
>
> return pct;
> }
> +
> +static int all_zero(unsigned long long *vals, int len)
> +{
> + int i;
> +
> + for (i = 0; i < len; i++)
> + if (vals[i] != 0)
> + return 0;
> + return 1;
> +}
> +
> +void print_stat_spark(FILE *f, struct stats *stat)
> +{
> + int len;
> +
> + if (stat->n <= 1)
> + return;
> +
> + len = stat->n;
> + if (len > NUM_SPARK_VALS)
> + len = NUM_SPARK_VALS;
> + if (all_zero(stat->svals, len))
> + return;
> +
> + print_spark(f, stat->svals, len);
> + if (stat->n > NUM_SPARK_VALS)
> + fputs("..", f);
> +}
> diff --git a/tools/perf/util/stat.h b/tools/perf/util/stat.h
> index 5667fc3..a049f03 100644
> --- a/tools/perf/util/stat.h
> +++ b/tools/perf/util/stat.h
> @@ -1,12 +1,16 @@
> #ifndef __PERF_STATS_H
> #define __PERF_STATS_H
>
> +#include <stdio.h>
> #include <linux/types.h>
>
> +#define NUM_SPARK_VALS 8 /* support spark line on first N items */
> +
> struct stats
> {
> double n, mean, M2;
> u64 max, min;
> + unsigned long long svals[NUM_SPARK_VALS];
> };
The structure's increasing size justifies proper vertical alignment.
>
> void update_stats(struct stats *stats, u64 val);
> @@ -14,12 +18,18 @@ double avg_stats(struct stats *stats);
> double stddev_stats(struct stats *stats);
> double rel_stddev_stats(double stddev, double avg);
>
> +void print_stat_spark(FILE *f, struct stats *stat);
> +
> static inline void init_stats(struct stats *stats)
> {
> + int i;
> +
> stats->n = 0.0;
> stats->mean = 0.0;
> stats->M2 = 0.0;
> stats->min = (u64) -1;
> stats->max = 0;
> + for (i = 0; i < NUM_SPARK_VALS; i++)
> + stats->svals[i] = 0;
memset(), or introduce a new helper, memclear_struct():
#define memclear_struct(struct_ptr) memset(struct_ptr, 0, sizeof(*(struct_ptr)))
Also, init_stats() should now probably move into util/stat.c. (in a
separate patch preparing these changes.)
Thanks,
Ingo
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