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Message-ID: <158894311353.8414.9179805955534572305.tip-bot2@tip-bot2>
Date: Fri, 08 May 2020 13:05:13 -0000
From: "tip-bot2 for Jin Yao" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Jin Yao <yao.jin@...ux.intel.com>, Jiri Olsa <jolsa@...hat.com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Andi Kleen <ak@...ux.intel.com>, Jin Yao <yao.jin@...el.com>,
Kan Liang <kan.liang@...ux.intel.com>,
Peter Zijlstra <peterz@...radead.org>,
Arnaldo Carvalho de Melo <acme@...hat.com>,
x86 <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [tip: perf/core] perf stat: Improve runtime stat for interval mode
The following commit has been merged into the perf/core branch of tip:
Commit-ID: 197ba86fdc888dc0d3d6b89b402c9c6851d4c6fb
Gitweb: https://git.kernel.org/tip/197ba86fdc888dc0d3d6b89b402c9c6851d4c6fb
Author: Jin Yao <yao.jin@...ux.intel.com>
AuthorDate: Mon, 20 Apr 2020 22:54:17 +08:00
Committer: Arnaldo Carvalho de Melo <acme@...hat.com>
CommitterDate: Thu, 23 Apr 2020 11:03:46 -03:00
perf stat: Improve runtime stat for interval mode
For interval mode, the metric is printed after the '#' character if it
exists. But it's not calculated by the counts generated in this
interval.
See the following examples:
root@...-ppc:~# perf stat -M CPI -I1000 --interval-count 2
# time counts unit events
1.000422803 764,809 inst_retired.any # 2.9 CPI
1.000422803 2,234,932 cycles
2.001464585 1,960,061 inst_retired.any # 1.6 CPI
2.001464585 4,022,591 cycles
The second CPI should not be 1.6 (4,022,591/1,960,061 is 2.1)
root@...-ppc:~# perf stat -e cycles,instructions -I1000 --interval-count 2
# time counts unit events
1.000429493 2,869,311 cycles
1.000429493 816,875 instructions # 0.28 insn per cycle
2.001516426 9,260,973 cycles
2.001516426 5,250,634 instructions # 0.87 insn per cycle
The second 'insn per cycle' should not be 0.87 (5,250,634/9,260,973 is
0.57).
The current code uses a global variable 'rt_stat' for tracking and
updating the std dev of runtime stat. Unlike the counts, 'rt_stat' is not
reset for interval. While the counts are reset for interval.
perf_stat_process_counter()
{
if (config->interval)
init_stats(ps->res_stats);
}
So for interval mode, the 'rt_stat' variable should be reset too.
This patch resets 'rt_stat' before read_counters(), so the runtime stat
is only calculated by the counts generated in this interval.
With this patch:
root@...-ppc:~# perf stat -M CPI -I1000 --interval-count 2
# time counts unit events
1.000420924 2,408,818 inst_retired.any # 2.1 CPI
1.000420924 5,010,111 cycles
2.001448579 2,798,407 inst_retired.any # 1.6 CPI
2.001448579 4,599,861 cycles
root@...-ppc:~# perf stat -e cycles,instructions -I1000 --interval-count 2
# time counts unit events
1.000428555 2,769,714 cycles
1.000428555 774,462 instructions # 0.28 insn per cycle
2.001471562 3,595,904 cycles
2.001471562 1,243,703 instructions # 0.35 insn per cycle
Now the second 'insn per cycle' and CPI are calculated by the counts
generated in this interval.
Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
Acked-by: Jiri Olsa <jolsa@...hat.com>
Tested-By: Kajol Jain <kjain@...ux.ibm.com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Jin Yao <yao.jin@...el.com>
Cc: Kan Liang <kan.liang@...ux.intel.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Link: http://lore.kernel.org/lkml/20200420145417.6864-1-yao.jin@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
tools/perf/Documentation/perf-stat.txt | 2 ++
tools/perf/builtin-stat.c | 1 +
2 files changed, 3 insertions(+)
diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
index 4d56586..3fb5028 100644
--- a/tools/perf/Documentation/perf-stat.txt
+++ b/tools/perf/Documentation/perf-stat.txt
@@ -176,6 +176,8 @@ Print count deltas every N milliseconds (minimum: 1ms)
The overhead percentage could be high in some cases, for instance with small, sub 100ms intervals. Use with caution.
example: 'perf stat -I 1000 -e cycles -a sleep 5'
+If the metric exists, it is calculated by the counts generated in this interval and the metric is printed after #.
+
--interval-count times::
Print count deltas for fixed number of times.
This option should be used together with "-I" option.
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 9207b6c..3f050d8 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -359,6 +359,7 @@ static void process_interval(void)
clock_gettime(CLOCK_MONOTONIC, &ts);
diff_timespec(&rs, &ts, &ref_time);
+ perf_stat__reset_shadow_per_stat(&rt_stat);
read_counters(&rs);
if (STAT_RECORD) {
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