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Re: [PATCH v3 5/5] perf/sdt: Add support to perf record to trace SDT events
- From: Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>
- To: Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>
- Cc: Hemant Kumar <hemant at linux dot vnet dot ibm dot com>, linux-kernel at vger dot kernel dot org, peterz at infradead dot org, oleg at redhat dot com, hegdevasant at linux dot vnet dot ibm dot com, mingo at redhat dot com, anton at redhat dot com, systemtap at sourceware dot org, namhyung at kernel dot org, aravinda at linux dot vnet dot ibm dot com, penberg at iki dot fi
- Date: Thu, 23 Oct 2014 11:24:22 +0530
- Subject: Re: [PATCH v3 5/5] perf/sdt: Add support to perf record to trace SDT events
- Authentication-results: sourceware.org; auth=none
- References: <20141010104402 dot 15506 dot 73285 dot stgit at hemant-fedora> <20141010105914 dot 15506 dot 84827 dot stgit at hemant-fedora> <54475292 dot 20409 at hitachi dot com> <544768C6 dot 6090105 at linux dot vnet dot ibm dot com> <54477BE6 dot 2060006 at hitachi dot com>
- Reply-to: Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>
* Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> [2014-10-22 18:41:58]:
> (2014/10/22 17:20), Hemant Kumar wrote:
> >>> From "file_sdt_ent" we will find out the file name.
> >>> Convert this sdt note into a perf event and then write this into uprobe_events
> >>> file to be able to record the event.
> >>> Then, corresponding entries are added to uprobe_events file for
> >>> the SDT events.
> >>> After recording is done, these events are silently deleted from uprobe_events
> >>> file. The uprobe_events file is present in debugfs/tracing directory.
> >>>
> >>> To support the addition and deletion of SDT events to/from uprobe_events
> >>> file, a record_sdt struct is maintained which has the event data.
> >> OK, I have some comments on this.
> >>
> >>> An example usage:
> >>>
> >>> # ./perf record -e %user_app:fun_start -aR /home/user_app
> >> At first, I'd like to add SDT support for adding probes too, like below;
> >>
> >> ./perf probe -a '%user_app:fun_start $vars'
> >
> > But I think, previously we discussed that we won't be having "perf
> > probe" for SDT events.
> > We list them and probe/trace them using "perf record" directly.
>
> Right, sorry for confusing you. I meant that I'd like to support SDT on both of
> perf-record and perf-probe :)
> And even if we'll hide sdt related events via perf, users can access it via ftrace.
> So, I doubt that we can completely hide them, in that case, honesty is the best way;)
>
I am somehow not able to figure out how perf probe comes into the
current workflow.
I think the current design was
1. perf sdt-cache --add <file> (only once per file)
2. perf record -e <sdt-event>
So what is the additional thing that perf probe does or Is it going to
replace any of the above steps?
--
Thanks and Regards
Srikar Dronamraju