Messages in this thread | | | Date | Thu, 27 Jun 2013 07:56:57 -0600 | From | David Ahern <> | Subject | Re: [PATCH 06/19] perf ftrace: Add support for --pid option |
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On 6/26/13 11:23 PM, Namhyung Kim wrote: > On Wed, 26 Jun 2013 11:12:19 -0600, David Ahern wrote: >> On 6/26/13 1:14 AM, Namhyung Kim wrote: >>> @@ -196,6 +222,8 @@ int cmd_ftrace(int argc, const char **argv, const char *prefix __maybe_unused) >>> const struct option ftrace_options[] = { >>> OPT_STRING('t', "tracer", &ftrace.tracer, "tracer", >>> "tracer to use"), >>> + OPT_STRING('p', "pid", &ftrace.target.tid, "pid", >>> + "trace on existing process id"), >>> OPT_INCR('v', "verbose", &verbose, >>> "be more verbose"), >>> OPT_END() >> >> You are calling it pid but assigning it as a tid which is inconsistent >> with other perf commands. e.g., perf-record allows a list of pids (-p) >> or tids (-t). Why not support that in perf-ftrace? And that leads to >> the comment about consistency of options across perf commands: -t is >> used here for tracer type to use. > > Sorry, I should've mentioned it. > > The pid filtering in ftrace is done via set_ftrace_pid file under the > tracing debugfs directory. IIRC It only supports process filtering not > thread filtering by iterating all threads in the kernel code. So --tid > option cannot be implemented as other perf commands. > > So I chose not to and assigned -t option to --tracer.
Could that ever change? With the current code why call it pid in the option but assign it to target.tid? Seems a like a source for confusion later. Would be better to just assign to target.pid and let the machinery do the right thing.
David
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