Messages in this thread Patch in this message | | | From | Andi Kleen <> | Subject | [PATCH] perf, tools: Add PERF_PID | Date | Tue, 19 Aug 2014 05:02:22 -0700 |
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From: Andi Kleen <ak@linux.intel.com>
It's currently difficult to filter out perf itself using a filter. This can give cascading effects during IO tracing when the IO perf does itself causes more trace output.
The best way to filter is to use the pid. But it's difficult to get the pid of perf without using hacks.
Add a PERF_PID meta variable to the perf filter that contains the current pid.
With this patch the following works
% perf record -e syscalls:sys_enter_write -a --filter 'common_pid != PERF_PID' ...
This won't work for more complex perf pipe lines with multiple processes, but at least solves the problem nicely for a single perf.
v2: Remove debug code. Don't use zero padding (Namhyung) Acked-by: Namhyung Kim <namhyung@kernel.org> Signed-off-by: Andi Kleen <ak@linux.intel.com> --- tools/perf/Documentation/perf-record.txt | 2 +- tools/perf/util/parse-events.c | 9 +++++++++ 2 files changed, 10 insertions(+), 1 deletion(-)
diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt index d460049..b6c5e51 100644 --- a/tools/perf/Documentation/perf-record.txt +++ b/tools/perf/Documentation/perf-record.txt @@ -41,7 +41,7 @@ OPTIONS 'mem:0x1000:rw'. --filter=<filter>:: - Event filter. + Event filter. PERF_PID represents the perf pid. -a:: --all-cpus:: diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c index 1e15df1..90ed63f 100644 --- a/tools/perf/util/parse-events.c +++ b/tools/perf/util/parse-events.c @@ -967,6 +967,7 @@ int parse_filter(const struct option *opt, const char *str, { struct perf_evlist *evlist = *(struct perf_evlist **)opt->value; struct perf_evsel *last = NULL; + char *pid; if (evlist->nr_entries > 0) last = perf_evlist__last(evlist); @@ -983,6 +984,14 @@ int parse_filter(const struct option *opt, const char *str, return -1; } + /* Assume a pid has not more than 8 characters */ + pid = strstr(last->filter, "PERF_PID"); + if (pid) { + char buf[9]; + snprintf(buf, 9, "%08d", getpid()); + memcpy(pid, buf, 8); + } + fprintf(stderr, "filter |%s|\n", last->filter); return 0; } -- 1.9.3
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