Hi Andi,
On Wed, 13 Aug 2014 14:12:17 -0700, Andi Kleen wrote:
> From: Andi Kleen <a...@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.
>
> Signed-off-by: Andi Kleen <a...@linux.intel.com>
I like the idea, so with comments below fixed:
Acked-by: Namhyung Kim <namhy...@kernel.org>
Thanks,
Namhyung
[SNIP]
> + /* 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());
Why do you add zero-paddings? I guess it'd confuse the parser as if
it's an octal digits. What about just using "%8d"? It seems the parser
ignores whitespaces between tokens..
> + memcpy(pid, buf, 8);
> + }
> + fprintf(stderr, "filter |%s|\n", last->filter);
Isn't it a debug message?
Thanks,
Namhyung
> return 0;
> }
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
