path: root/Documentation/trace/coresight.txt
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authorRobert Walker <robert.walker@arm.com>2018-02-14 11:24:41 +0000
committerArnaldo Carvalho de Melo <acme@redhat.com>2018-02-16 14:55:46 -0300
commit6673016f874adee171690f95540ead5efddb5351 (patch)
treec86c245bc9bf62b10d73bc392c29672aaec6d0a9 /Documentation/trace/coresight.txt
parent256e751cac78739a4de2232450d3681b68b5845e (diff)
coresight: Update documentation for perf usage
Add notes on using perf to collect and analyze CoreSight trace Signed-off-by: Robert Walker <robert.walker@arm.com> Cc: Mathieu Poirier <mathieu.poirier@linaro.org> Cc: coresight@lists.linaro.org Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/1518607481-4059-4-git-send-email-robert.walker@arm.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'Documentation/trace/coresight.txt')
1 files changed, 51 insertions, 0 deletions
diff --git a/Documentation/trace/coresight.txt b/Documentation/trace/coresight.txt
index a33c88cd5d1d..6f0120c3a4f1 100644
--- a/Documentation/trace/coresight.txt
+++ b/Documentation/trace/coresight.txt
@@ -330,3 +330,54 @@ Details on how to use the generic STM API can be found here [2].
[1]. Documentation/ABI/testing/sysfs-bus-coresight-devices-stm
[2]. Documentation/trace/stm.txt
+Using perf tools
+perf can be used to record and analyze trace of programs.
+Execution can be recorded using 'perf record' with the cs_etm event,
+specifying the name of the sink to record to, e.g:
+ perf record -e cs_etm/@20070000.etr/u --per-thread
+The 'perf report' and 'perf script' commands can be used to analyze execution,
+synthesizing instruction and branch events from the instruction trace.
+'perf inject' can be used to replace the trace data with the synthesized events.
+The --itrace option controls the type and frequency of synthesized events
+(see perf documentation).
+Note that only 64-bit programs are currently supported - further work is
+required to support instruction decode of 32-bit Arm programs.
+Generating coverage files for Feedback Directed Optimization: AutoFDO
+'perf inject' accepts the --itrace option in which case tracing data is
+removed and replaced with the synthesized events. e.g.
+ perf inject --itrace --strip -i perf.data -o perf.data.new
+Below is an example of using ARM ETM for autoFDO. It requires autofdo
+(https://github.com/google/autofdo) and gcc version 5. The bubble
+sort example is from the AutoFDO tutorial (https://gcc.gnu.org/wiki/AutoFDO/Tutorial).
+ $ gcc-5 -O3 sort.c -o sort
+ $ taskset -c 2 ./sort
+ Bubble sorting array of 30000 elements
+ 5910 ms
+ $ perf record -e cs_etm/@20070000.etr/u --per-thread taskset -c 2 ./sort
+ Bubble sorting array of 30000 elements
+ 12543 ms
+ [ perf record: Woken up 35 times to write data ]
+ [ perf record: Captured and wrote 69.640 MB perf.data ]
+ $ perf inject -i perf.data -o inj.data --itrace=il64 --strip
+ $ create_gcov --binary=./sort --profile=inj.data --gcov=sort.gcov -gcov_version=1
+ $ gcc-5 -O3 -fauto-profile=sort.gcov sort.c -o sort_autofdo
+ $ taskset -c 2 ./sort_autofdo
+ Bubble sorting array of 30000 elements
+ 5806 ms