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Re: [RFC PATCH v1 0/2] perf: Support for SDT markers


On 02/26/2014 03:12 PM, Masami Hiramatsu wrote:
(2014/02/26 18:03), Hemant Kumar wrote:
On 02/26/2014 01:48 PM, Namhyung Kim wrote:
Hi Masami and Hemant,

On Tue, 25 Feb 2014 21:27:07 +0530, Hemant Kumar wrote:
On 02/25/2014 05:14 PM, Masami Hiramatsu wrote:
(2014/02/24 18:14), Hemant Kumar wrote:
First, scan the binaries using :
# perf list sdt --scan

Creating a cache of SDT markers...
perf sdt cache created!
    Use : "perf list sdt"
    to see the SDT markers
Hmm, in that case, I think you'd better introduce perf-sdt for scanning.
e.g.

    # perf sdt --scan app
Hmm, this seems a better idea :)

    then you can add app to sdt cache, without app,

    # perf sdt --scan

    will just scans all binaries on the PATH and the libraries which listed
by `ldconfig --print-caceh`
What should be done with the new perf sdt command?  If it's only
intended to list the markers, I'd just suggest to add "perf list sdt" as
this patch did.
No, here what I said is, the "perf sdt" is only for managing SDT cache
as like as "perf buildid-cache". Thus, "perf sdt-cache" might be better.

Ah! ok.

BTW, the SDT markers can be changed if the application is updated.
To ensure the correctness of SDT markers, we should store buildid in the
cache file and check it when listing and using them.

Yeah! That's why perf list sdt --scan is storing the buildid too in the cache file.

If we display the SDT markers along with the other events in perf list,
then I think we can go with
perf list sdt. I am not too sure though! :)

For me, the main issue was that the markers are not events. They become
events after
we place them in the uprobe_events file just like functions.  But we use
`perf list` to
display all the "events" available on a system. Isn't it?
As I said, if perf accepts -e "%app:sdt" option, showing SDT events as
fixed events does not matter, since it is transparent to users. :)

Thank you,


Alright. Got it! :)

--
Thanks
Hemant Kumar


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