linux-kernel - Re: [PATCH perf/core 00/22] perf refcnt debugger API and fixes

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Message-ID: <566A2CA0.8070608@huawei.com>
Date:	Fri, 11 Dec 2015 09:53:36 +0800
From:	"Wangnan (F)" <wangnan0@...wei.com>
To:	"'Arnaldo Carvalho de Melo'" <acme@...nel.org>
CC:	平松雅巳 / HIRAMATU，MASAMI 
	<masami.hiramatsu.pt@...achi.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	"Namhyung Kim" <namhyung@...nel.org>, Jiri Olsa <jolsa@...hat.com>,
	Alexei Starovoitov <ast@...mgrid.com>
Subject: Re: [PATCH perf/core  00/22] perf refcnt debugger API and fixes



On 2015/12/10 23:12, 'Arnaldo Carvalho de Melo' wrote:

[SNIP]
> But this requires having these special refcnt__ routines, that will make
> tools/perf/ code patterns for reference counts look different that the
> refcount patterns in the kernel :-\
>
> And would be a requirement to change the observed workload :-\
>
> Is this _strictly_ required?

No. The requirement should be:

  1. The create/get/put/delete functions are non-inline (because dwarf info
     is not as reliable as symbol);
  2. From their argument list, we can always get the variable we need (the
     pointer of objects, the value of refcnt, etc.)

We don't have to use this refcnt things.

> Can't we, for a project like perf, where we
> know where some refcount (say, the one for 'struct thread') gets
> initialized, use that (thread__new()) and then hook into thread__get and
> thread__put and then use the destructor, thread__delete() as the place
> to dump leaks?
>

I think it is possible. If we can abstract a common pattern about it,
we can provide a perf subcommand which we can deal with generic alloc/free
pattern. I'll put it on my todo-list. Currently we are focusing on perf
daemonization.

Thank you.

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