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perf intel-pt: Document snapshot control command

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The documentation describes snapshot mode.  Update it to include the new
snapshot control command.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Alexey Budankov <alexey.budankov@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lore.kernel.org/lkml/20200901093758.32293-7-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Adrian Hunter 2020-09-01 12:37:58 +03:00 committed by Arnaldo Carvalho de Melo
parent 0b157b1000
commit 9818923634
1 changed files with 20 additions and 3 deletions
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23
tools/perf/Documentation/perf-intel-pt.txt
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@ -558,7 +558,7 @@ The mmap size and auxtrace mmap size are displayed if the -vv option is used e.g
Intel PT modes of operation
~~~~~~~~~~~~~~~~~~~~~~~~~~~
Intel PT can be used in 2 modes:
Intel PT can be used in 3 modes:
full-trace mode
sample mode
snapshot mode
@ -571,7 +571,8 @@ Sample mode attaches a Intel PT sample to other events e.g.
perf record --aux-sample -e intel_pt//u -e branch-misses:u
Snapshot mode captures the available data when a signal is sent e.g.
Snapshot mode captures the available data when a signal is sent or "snapshot"
control command is issued. e.g. using a signal
perf record -v -e intel_pt//u -S ./loopy 1000000000 &
[1] 11435
@ -582,7 +583,23 @@ Note that the signal sent is SIGUSR2.
Note that "Recording AUX area tracing snapshot" is displayed because the -v
option is used.
The 2 modes cannot be used together.
The advantage of using "snapshot" control command is that the access is
controlled by access to a FIFO e.g.
$ mkfifo perf.control
$ mkfifo perf.ack
$ cat perf.ack &
[1] 15235
$ sudo ~/bin/perf record --control fifo:perf.control,perf.ack -S -e intel_pt//u -- sleep 60 &
[2] 15243
$ ps -e | grep perf
15244 pts/1 00:00:00 perf
$ kill -USR2 15244
bash: kill: (15244) - Operation not permitted
$ echo snapshot > perf.control
ack
The 3 Intel PT modes of operation cannot be used together.
Buffer handling