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From: Andi Kleen <ak@linux.intel.com>
To: Ben Gainey <ben.gainey@arm.com>
Cc: linux-perf-users@vger.kernel.org,  linux-kernel@vger.kernel.org,
  peterz@infradead.org,  mingo@redhat.com,  acme@kernel.org,
  mark.rutland@arm.com,  alexander.shishkin@linux.intel.com,
  jolsa@kernel.org,  namhyung@kernel.org,  irogers@google.com,
  adrian.hunter@intel.com,  james.clark@arm.com
Subject: Re: [PATCH 0/1] Support PERF_SAMPLE_READ with inherit_stat
In-Reply-To: <20240119163924.2801678-1-ben.gainey@arm.com> (Ben Gainey's
	message of "Fri, 19 Jan 2024 16:39:23 +0000")
References: <20240119163924.2801678-1-ben.gainey@arm.com>
Date: Fri, 19 Jan 2024 09:45:44 -0800
Message-ID: <87a5p1kyif.fsf@linux.intel.com>
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Ben Gainey <ben.gainey@arm.com> writes:

> In this configuration stream ids (such as may appear in the read_format 
> field of a PERF_RECORD_SAMPLE) are no longer globally unique, rather 
> the pair of (stream id, tid) uniquely identify each event. Tools that 
> rely on this, for example to calculate a delta between samples, would 
> need updating to take this into account. Previously valid event 
> configurations (system-wide, no-inherit and so on) where each stream id 
> is the identifier are unaffected.

So is this an ABI break? It might need an optin, if it breaks anything,
which wouldn't surprise me. We do have a lot of different perf stream
parsers around these days and we cannot break them.

-Andi