perf record: Allow filtering perf's pid via --exclude-perf

This patch allows 'perf record' to exclude events issued by perf itself
by '--exclude-perf' option.

Before this patch, when doing something like:

 # perf record -a -e syscalls:sys_enter_write <cmd>

One could easily get result like this:

 # /tmp/perf report --stdio
 ...
  # Overhead  Command  Shared Object       Symbol
  # ........  .......  ..................  ....................
  #
      99.99%  perf     libpthread-2.18.so  [.] __write_nocancel
      0.01%   ls       libc-2.18.so        [.] write
      0.01%   sshd     libc-2.18.so        [.] write
 ...

Where most events are generated by perf itself.

A shell trick can be done to filter perf itself out:

 # cat << EOF > ./tmp
 > #!/bin/sh
 > exec perf record -e ... --filter="common_pid != \$\$" -a sleep 10
 > EOF
 # chmod a+x ./tmp
 # ./tmp

However, doing so is user unfriendly.

This patch extracts evsel iteration framework introduced by patch 'perf
record: Apply filter to all events in a glob matching' into
foreach_evsel_in_last_glob(), and makes exclude_perf() function append
new filter expression to each evsel selected by a '-e' selector.

To avoid losing filters if user pass '--filter' after '--exclude-perf',
this patch uses perf_evsel__append_filter() in both case, instead of
perf_evsel__set_filter() which removes old filter. As a side effect, now
it is possible to use multiple '--filter' option for one selector. They
are combinded with '&&'.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1436513770-8896-2-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 5b47b2c88223..29e5307945bf 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -69,7 +69,16 @@ OPTIONS
 	  "perf report" to view group events together.
 
 --filter=<filter>::
-        Event filter.
+        Event filter. This option should follow a event selector (-e) which
+	selects tracepoint event(s). Multiple '--filter' options are combined
+	using '&&'.
+
+--exclude-perf::
+	Don't record events issued by perf itself. This option should follow
+	a event selector (-e) which selects tracepoint event(s). It adds a
+	filter expression 'common_pid != $PERFPID' to filters. If other
+	'--filter' exists, the new filter expression will be combined with
+	them by '&&'.
 
 -a::
 --all-cpus::