From: Jiri Olsa <jolsa@redhat.com>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: Jiri Olsa <jolsa@kernel.org>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: perf stat stddev reporting broken since "perf stat: Introduce read_counters function"
Date: Tue, 19 Jan 2016 08:42:28 +0100 [thread overview]
Message-ID: <20160119074228.GB20358@krava.brq.redhat.com> (raw)
In-Reply-To: <20160118175946.GC10802@techsingularity.net>
On Mon, Jan 18, 2016 at 05:59:46PM +0000, Mel Gorman wrote:
> I noticed that perf stat in 4.4 is not printing stddev figures as
> expected and bisected it to commit 106a94a0f8c2 ("perf stat: Introduce
> read_counters function").
>
> # Kernel 4.4
> # make clean && make prefix=/usr && ./perf stat -r 5 sleep 1
> Performance counter stats for 'sleep 1' (5 runs):
>
> 0.466683 task-clock (msec) # 0.000 CPUs utilized
> 1 context-switches # 0.002 M/sec
> 1 cpu-migrations # 0.002 M/sec
> 66 page-faults # 0.144 M/sec
> 1,630,220 cycles # 3.562 GHz
> <not supported> stalled-cycles-frontend
> <not supported> stalled-cycles-backend
> 902,686 instructions # 0.66 insns per cycle
> 185,692 branches # 405.786 M/sec
> 8,640 branch-misses # 4.63% of all branches
>
> 1.000855883 seconds time elapsed ( +- 0.01% )
>
> # git checkout 106a94a0f8c207ef4113ce7e32f34a00b3b174e7^
> Performance counter stats for 'sleep 1' (5 runs):
>
> 0.397939 task-clock (msec) # 0.000 CPUs utilized ( +- 3.37% )
> 1 context-switches # 0.003 M/sec
> 0 cpu-migrations # 0.000 K/sec
> 67 page-faults # 0.169 M/sec ( +- 0.56% )
> 1,360,763 cycles # 3.420 GHz ( +- 2.14% )
> <not supported> stalled-cycles-frontend
> <not supported> stalled-cycles-backend
> 903,901 instructions # 0.66 insns per cycle ( +- 0.24% )
> 186,472 branches # 468.595 M/sec ( +- 0.29% )
> 8,599 branch-misses # 4.61% of all branches ( +- 0.77% )
>
> 1.000761882 seconds time elapsed ( +- 0.00% )
>
> # git checkout 106a94a0f8c207ef4113ce7e32f34a00b3b174e7
>
> Performance counter stats for 'sleep 1' (5 runs):
>
> 0.583178 task-clock (msec) # 0.001 CPUs utilized
> 1 context-switches # 0.002 M/sec
> 0 cpu-migrations # 0.000 K/sec
> 67 page-faults # 0.141 M/sec
> 1,224,416 cycles # 2.585 GHz
> <not supported> stalled-cycles-frontend
> <not supported> stalled-cycles-backend
> 892,568 instructions # 0.68 insns per cycle
> 184,975 branches # 390.554 M/sec
> 8,512 branch-misses # 4.57% of all branches
>
> 1.000889249 seconds time elapsed ( +- 0.01% )
>
> I checked and current master in Linus' tree is also broken. Is this
> change in documented perf stat behaviour intentional?
nope, not intentional.. I'll check on that, thanks for reporting
jirka
next prev parent reply other threads:[~2016-01-19 7:42 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-18 17:59 Mel Gorman
2016-01-19 7:42 ` Jiri Olsa [this message]
2016-01-19 8:16 ` Jiri Olsa
2016-01-19 9:38 ` Mel Gorman
2016-01-19 9:57 ` Jiri Olsa
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