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authorAdrian Hunter <adrian.hunter@intel.com>2015-09-25 16:15:45 +0300
committerArnaldo Carvalho de Melo <acme@redhat.com>2015-09-28 16:59:14 -0300
commitf14445ee72c59f32aa5cbf4d0f0330a5f62a752d (patch)
tree6498ddc2acfef1a06f1b5cf10606b8f1171dbc9e /tools/perf/Documentation/intel-pt.txt
parent385e33063fb963f5cccb0a37fe539319b6481fa5 (diff)
downloadop-kernel-dev-f14445ee72c59f32aa5cbf4d0f0330a5f62a752d.zip
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perf intel-pt: Support generating branch stack
Add support for generating branch stack context for PT samples. The decoder reports a configurable number of branches as branch context for each sample. Internally it keeps track of them by using a simple sliding window. We also flush the last branch buffer on each sample to avoid overlapping intervals. This is useful for: - Reporting accurate basic block edge frequencies through the perf report branch view - Using with --branch-history to get the wider context of samples - Other users of LBRs Also the Documentation is updated. Examples: Record with Intel PT: perf record -e intel_pt//u ls Branch stacks are used by default if synthesized so: perf report --itrace=ile is the same as: perf report --itrace=ile -b Branch history can be requested also: perf report --itrace=igle --branch-history Based-on-patch-by: Andi Kleen <ak@linux.intel.com> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Cc: Jiri Olsa <jolsa@redhat.com> Link: http://lkml.kernel.org/r/1443186956-18718-15-git-send-email-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools/perf/Documentation/intel-pt.txt')
-rw-r--r--tools/perf/Documentation/intel-pt.txt10
1 files changed, 10 insertions, 0 deletions
diff --git a/tools/perf/Documentation/intel-pt.txt b/tools/perf/Documentation/intel-pt.txt
index 886612b..a0fbb5d 100644
--- a/tools/perf/Documentation/intel-pt.txt
+++ b/tools/perf/Documentation/intel-pt.txt
@@ -671,6 +671,7 @@ The letters are:
e synthesize tracing error events
d create a debug log
g synthesize a call chain (use with i or x)
+ l synthesize last branch entries (use with i or x)
"Instructions" events look like they were recorded by "perf record -e
instructions".
@@ -718,6 +719,15 @@ transactions events can be specified. e.g.
--itrace=ig32
--itrace=xg32
+Also the number of last branch entries (default 64, max. 1024) for instructions or
+transactions events can be specified. e.g.
+
+ --itrace=il10
+ --itrace=xl10
+
+Note that last branch entries are cleared for each sample, so there is no overlap
+from one sample to the next.
+
To disable trace decoding entirely, use the option --no-itrace.
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