Commit 082ab9a1 authored Jul 20, 2017 by Arnaldo Carvalho de Melo

perf trace: Filter out 'sshd' in the tracer ancestry in syswide tracing

Avoiding a loop, so now its quite convenient to ssh to a machine and
then simply do:

	# perf trace

To trace all syscalls without causing a loop.

This was possible using --filter-pids, i.e. once you noticed the loop,
get the sshd pid and add it to --filter-pids, restarting the 'perf
trace'.

Now to figure out how to do that in a X terminal, the other common
scenario, which is way more involved, as there are multiple processes
communicating to process terminal activity...

Using --filter-pids + '-e \!syscall,names,you,dont,need' may be a good
approximation when having to do syswide tracing on your workstation.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-68rjeao9wnpylla41htk7xps@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

parent dd1a5037

tools/perf/builtin-trace.c

+15 −1

Original line number	Diff line number	Diff line
		@@ -2241,10 +2241,24 @@ static int trace__set_ev_qualifier_filter(struct trace *trace)

		static int trace__set_filter_loop_pids(struct trace *trace)
		{
		int nr = 1;
		unsigned int nr = 1;
		pid_t pids[32] = {
		getpid(),
		};
		struct thread *thread = machine__find_thread(trace->host, pids[0], pids[0]);

		while (thread && nr < ARRAY_SIZE(pids)) {
		struct thread *parent = machine__find_thread(trace->host, thread->ppid, thread->ppid);

		if (parent == NULL)
		break;

		if (!strcmp(thread__comm_str(parent), "sshd")) {
		pids[nr++] = parent->tid;
		break;
		}
		thread = parent;
		}

		return perf_evlist__set_filter_pids(trace->evlist, nr, pids);
		}