From: Mel Gorman <mgorman@techsingularity.net>
To: Jiri Olsa <jolsa@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: perf stat stddev reporting broken since "perf stat: Introduce read_counters function"
Date: Mon, 18 Jan 2016 17:59:46 +0000 [thread overview]
Message-ID: <20160118175946.GC10802@techsingularity.net> (raw)
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?
--
Mel Gorman
SUSE Labs
next reply other threads:[~2016-01-18 17:59 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-18 17:59 Mel Gorman [this message]
2016-01-19 7:42 ` Jiri Olsa
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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