Commit 98189236 authored by Adrian Hunter's avatar Adrian Hunter Committed by Arnaldo Carvalho de Melo
Browse files

perf intel-pt: Document snapshot control command 



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

Signed-off-by: default avatarAdrian Hunter <adrian.hunter@intel.com>
Acked-by: default avatarAlexey Budankov <alexey.budankov@linux.intel.com>
Acked-by: default avatarJiri 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: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 0b157b10

tools/perf/Documentation/perf-intel-pt.txt

+20 −3
Original line number Diff line number Diff line
@@ -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