72f02a947e
root@kbl-ppc:~# perf stat --per-thread -e cycles,instructions -I1000 --interval-count 2
1.004171683 perf-3696 8,747,311 cycles
...
1.004171683 perf-3696 691,730 instructions # 0.08 insn per cycle
...
2.006490373 perf-3696 1,749,936 cycles
...
2.006490373 perf-3696 1,484,582 instructions # 0.28 insn per cycle
...
Let's see interval 2.006490373
perf-3696 1,749,936 cycles
perf-3696 1,484,582 instructions # 0.28 insn per cycle
insn per cycle = 1,484,582 / 1,749,936 = 0.85.
But now it's 0.28, that's not correct.
stat_config.stats[] records the per-thread runtime stat. But for
interval mode, it should be reset for each interval.
So now, with this patch,
root@kbl-ppc:~# perf stat --per-thread -e cycles,instructions -I1000 --interval-count 2
1.005818121 perf-8633 9,898,045 cycles
...
1.005818121 perf-8633 693,298 instructions # 0.07 insn per cycle
...
2.007863743 perf-8633 1,551,619 cycles
...
2.007863743 perf-8633 1,317,514 instructions # 0.85 insn per cycle
...
Let's check interval 2.007863743.
insn per cycle = 1,317,514 / 1,551,619 = 0.85. It's correct.
This patch creates runtime_stat_reset, places it next to
untime_stat_new/runtime_stat_delete and moves all runtime_stat
functions before process_interval.
Committer testing:
After the patch:
# perf stat --per-thread -e cycles,instructions -I1000 --interval-count 2 |& grep sssd_nss-1130
2.011309774 sssd_nss-1130 56,585 cycles
2.011309774 sssd_nss-1130 13,121 instructions # 0.23 insn per cycle
# python
>>> 13121.0 / 56585
0.23188124061146947
>>>
Fixes: commit 14e72a21c783 ("perf stat: Update or print per-thread stats")
Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Reviewed-by: Jiri Olsa <jolsa@redhat.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jin Yao <yao.jin@intel.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20200520042737.24160-2-yao.jin@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.