linux-kernel - Re: [PATCH 33/40] perf session: Separate struct machines from session

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Date:	Tue, 19 May 2015 19:46:18 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Jiri Olsa <jolsa@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Andi Kleen <andi@...stfloor.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 33/40] perf session: Separate struct machines from session

Em Tue, May 19, 2015 at 04:28:15PM +0900, Namhyung Kim escreveu:
> On Mon, May 18, 2015 at 09:52:59AM -0300, Arnaldo Carvalho de Melo wrote:
> > Em Mon, May 18, 2015 at 09:30:48AM +0900, Namhyung Kim escreveu:
> > > With multi-thread report, separate sessions can be passed to each
> > > thread, in this case we should keep a single machine state for all
> > > struct sessions.  Separate machines and have a pointer in sessions.
> > 
> > I had to look at all the patch to semi-figure this out, i.e. you said it
> > should be separated from 'perf_session', agreed.
> > 
> > But who will create it?  How will it be passed to the perf_session
> > instances?
> > 
> > Most of the patch is making session->machines be turned into a pointer,
> > but the meat, i.e. who creates it, is unclear, I see a malloc in
> > perf_session__new(), where I was kinda expecting that a higer layer,
> > perhaps in struct tool? Would create the list of all machines (struct
> > machines) and then pass it to multiple perf_session__new() calls.
> > 
> > But then perf_session__delete() calls 'free(session->machines)', huh?
> 
> OK.  So, this is what I have in my head:
> 
>   perf_tool__create_machines(tool) {
>     tool->machines = malloc();
>     machines__init(tool->machines);
>   }


Probably, but then in this case you would call machines__new(), that
does the malloc and init.

> 
>   perf_session__new(file, repipe, tool) {
>     session->machines = tool->machines;
>     ...
>   }

That could be ok.

> 
>   perf_tool__delete_machines(tool) {
>     /* call machines-related destructors */
>     free(tool->machines);
>   }

That would be machines__delete(tool->machines), that calls
machine__exit() and then does the free.

- Arnaldo
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