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authorMichael Ellerman <michael@ellerman.id.au>2013-08-06 23:28:05 +1000
committerArnaldo Carvalho de Melo <acme@redhat.com>2013-08-07 17:35:40 -0300
commite9a7c414477d20c3cc56f90f29c35b06f0f15e25 (patch)
treea322f63cea50e67f997af05113a5024bf61aaf45 /tools/perf/Documentation/perf-list.txt
parentd50bf78ff69297d3f60aa778c272acc8e5f59a19 (diff)
downloadlinux-e9a7c414477d20c3cc56f90f29c35b06f0f15e25.tar.gz
perf tools: Add support for pinned modifier
This commit adds support for a new modifier "D", which requests that the event, or group of events, be pinned to the PMU. The "p" modifier is already taken for precise, and "P" may be used in future to mean "fully precise". So we use "D", which stands for pinneD - and looks like a padlock, or if you're using the ":D" syntax perf smiles at you. This is an oft-requested feature from our HW folks, who want to be able to run a large number of events, but also want 100% accurate results for instructions per cycle. Comparison of results with and without pinning: $ perf stat -e '{cycles,instructions}:D' -e cycles,instructions,... 79,590,480,683 cycles # 0.000 GHz 166,123,716,524 instructions # 2.09 insns per cycle # 0.11 stalled cycles per insn 79,352,134,463 cycles # 0.000 GHz [11.11%] 165,178,301,818 instructions # 2.08 insns per cycle # 0.11 stalled cycles per insn [11.13%] As you can see although perf does a very good job of scaling the values in the non-pinned case, there is some small discrepancy. The patch is fairly straight forward, the one detail is that we need to make sure we only request pinning for the group leader when we have a group. Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Acked-by: Namhyung Kim <namhyung@kernel.org> Acked-by: Jiri Olsa <jolsa@redhat.com> Tested-by: Jiri Olsa <jolsa@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1375795686-4226-1-git-send-email-michael@ellerman.id.au [ Use perf_evsel__is_group_leader instead of open coded equivalent, as suggested by Jiri Olsa ] Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools/perf/Documentation/perf-list.txt')
-rw-r--r--tools/perf/Documentation/perf-list.txt1
1 files changed, 1 insertions, 0 deletions
diff --git a/tools/perf/Documentation/perf-list.txt b/tools/perf/Documentation/perf-list.txt
index eb03f063f0a2..6fce6a622206 100644
--- a/tools/perf/Documentation/perf-list.txt
+++ b/tools/perf/Documentation/perf-list.txt
@@ -30,6 +30,7 @@ counted. The following modifiers exist:
H - host counting (not in KVM guests)
p - precise level
S - read sample value (PERF_SAMPLE_READ)
+ D - pin the event to the PMU
The 'p' modifier can be used for specifying how precise the instruction
address should be. The 'p' modifier can be specified multiple times: