linux-kernel - Re: [RFC] perf/sdt: Directly record SDT event with 'perf record'

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Date:   Mon, 20 Feb 2017 08:08:51 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Cc:     mingo@...hat.com, acme@...nel.org, masami.hiramatsu.pt@...achi.com,
        brendan.d.gregg@...il.com, peterz@...radead.org,
        alexander.shishkin@...ux.intel.com, wangnan0@...wei.com,
        jolsa@...nel.org, ak@...ux.intel.com, treeze.taeung@...il.com,
        mathieu.poirier@...aro.org, hekuang@...wei.com,
        sukadev@...ux.vnet.ibm.com, ananth@...ibm.com,
        naveen.n.rao@...ux.vnet.ibm.com, colin.ing@...onical.com,
        adrian.hunter@...el.com, linux-kernel@...r.kernel.org,
        hemant@...ux.vnet.ibm.com
Subject: Re: [RFC] perf/sdt: Directly record SDT event with 'perf record'


* Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com> wrote:

> All events from 'perf list', except SDT events, can be directly recorded
> with 'perf record'. But, the flow is little different for SDT events.
> Probe point for SDT event needs to be created using 'perf probe' before
> recording it using 'perf record'.
> 
> As suggested by Ingo[1], it's better to make this process simple by
> creating probe points automatically with 'perf record' for SDT events.
> 
> This patch disables 'perf probe' on SDT events to simplify usage. It
> enables recording SDT event only with 'perf record'.
> 
> This removes all those 'multiple events with same name' issues by not
> allowing manual probe creation to user. When there are multiple events
> with same name, 'perf record' will record all of them (in line with
> other tools supporting SDT (systemtap)).
> 
> I know 'perf probe' for SDT events has already became interface and
> people are using it. But, doing this change will make user interface very
> easy and also it will make tool behaviour consistent. Also, it won't
> require any changes in uprobe_events structure (suggested by Masami[2]).

So I like the automatism you implemented for 'perf record', but why not keep the 
'perf probe' flow as well, if people got used to it?

It's not like computer software is bad at sorting apart and handling the two cases 
properly, right?

Thanks,

	Ingo