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Date: Tue, 30 May 2017 06:57:14 -0700
From: Andi Kleen <ak@linux.intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, Vince Weaver <vince@deater.net>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
        Stephane Eranian <eranian@google.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Jiri Olsa <jolsa@kernel.org>
Subject: Re: perf group read for inherited events
Message-ID: <20170530135714.GJ24144@tassilo.jf.intel.com>
References: <20170526205601.GA5271@tassilo.jf.intel.com>
 <20170530094512.dy2nljns2uq7qa3j@hirez.programming.kicks-ass.net>
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On Tue, May 30, 2017 at 11:45:12AM +0200, Peter Zijlstra wrote:
> > Or is the simple patch below good enough?
> 
> The below seems to be the correct thing. It is rather unfortunate that
> this would break/significantly change existing semantics :/

The "existing semantics" as in ignoring the PERF_SAMPLE_READ in sample_type,
even though it wasn't implemented? It seems reasonable to me.

If you really worry about it could drop a printk_once in and see if it
triggers anywhere (and if yes drop the if completely)

The patch looks good to me. Please consider adding it.
I have some patches to use this in perf stat, will submit later.

-Andi