Re: user-defined static trace points

[Hemant Kumar <hemant@linux.vnet.ibm.com>]

On 03/02/2016 12:48 AM, Andi Kleen wrote:
> Milian Wolff <milian.wolff@kdab.com> writes:
>
>> Hey all,
>>
>> I'm aware that we can add custum user-defined dynamic trace points using `perf
>> probe`. But this is unwieldy for some larger applications, esp. if we
>> recompile them often. Is there a public API (that I could not find so far), to
>> define static trace points in userspace code?
>>
>> I found
>> http://www.brendangregg.com/blog/2015-07-03/hacking-linux-usdt-ftrace.html
>> which references https://www.sourceware.org/systemtap/wiki/
>> AddingUserSpaceProbingToApps for systemtap, but on my machine I don't have a
>> <sys/sdt.h> header.
> You need to install systemtap-devel or similar.
>
>> Would such trace points be useable by perf? https://
>> lwn.net/Articles/570818/ doesn't seem to be included, i.e. I don't have `perf
>> probe --markers` with a recent build of perf.
> There is a patch to teach perf about SDT probes, but so far it has not
> been integrated. You can use them from systemtap or gdb though.
>
> https://lwn.net/Articles/569622/
>
> Perhaps Hemant needs to resubmit?
>

So far, the patches for SDT support for perf have undergone several changes
and ultimately got picked up by Masami. Masami was working on the probe 
cache
feature along with the SDT support and sent a v3 :
https://lkml.org/lkml/2015/8/15/52
(" [RFC PATCH perf/core v3 00/17] perf-probe --cache and SDT support")

Although, I don't think the SDT related patches got picked up.

Masami, are you working on a v4 patchset?

-- 
Thanks,
Hemant Kumar