perf stat: Introduce --control fd:ctl-fd[,ack-fd] options

Introduce --control fd:ctl-fd[,ack-fd] options to pass open file
descriptors numbers from command line. Extend perf-stat.txt file with
--control fd:ctl-fd[,ack-fd] options description. Document possible
usage model introduced by --control fd:ctl-fd[,ack-fd] options by
providing example bash shell script.

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/feabd5cf-0155-fb0a-4587-c71571f2d517@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 39 insertions, 0 deletions

diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
index 9f32f6cd558d..c9bfefc051fb 100644
--- a/tools/perf/Documentation/perf-stat.txt
+++ b/tools/perf/Documentation/perf-stat.txt
@@ -176,6 +176,45 @@ with it.  --append may be used here.  Examples:
      3>results  perf stat --log-fd 3          -- $cmd
      3>>results perf stat --log-fd 3 --append -- $cmd
 
+--control fd:ctl-fd[,ack-fd]
+Listen on ctl-fd descriptor for command to control measurement ('enable': enable events,
+'disable': disable events). Measurements can be started with events disabled using
+--delay=-1 option. Optionally send control command completion ('ack\n') to ack-fd descriptor
+to synchronize with the controlling process. Example of bash shell script to enable and
+disable events during measurements:
+
+#!/bin/bash
+
+ctl_dir=/tmp/
+
+ctl_fifo=${ctl_dir}perf_ctl.fifo
+test -p ${ctl_fifo} && unlink ${ctl_fifo}
+mkfifo ${ctl_fifo}
+exec {ctl_fd}<>${ctl_fifo}
+
+ctl_ack_fifo=${ctl_dir}perf_ctl_ack.fifo
+test -p ${ctl_ack_fifo} && unlink ${ctl_ack_fifo}
+mkfifo ${ctl_ack_fifo}
+exec {ctl_fd_ack}<>${ctl_ack_fifo}
+
+perf stat -D -1 -e cpu-cycles -a -I 1000       \
+          --control fd:${ctl_fd},${ctl_fd_ack} \
+          -- sleep 30 &
+perf_pid=$!
+
+sleep 5  && echo 'enable' >&${ctl_fd} && read -u ${ctl_fd_ack} e1 && echo "enabled(${e1})"
+sleep 10 && echo 'disable' >&${ctl_fd} && read -u ${ctl_fd_ack} d1 && echo "disabled(${d1})"
+
+exec {ctl_fd_ack}>&-
+unlink ${ctl_ack_fifo}
+
+exec {ctl_fd}>&-
+unlink ${ctl_fifo}
+
+wait -n ${perf_pid}
+exit $?
+
+
 --pre::
 --post::
 	Pre and post measurement hooks, e.g.: