From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 142654F1FA; Fri, 19 Jan 2024 16:39:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705682393; cv=none; b=UuWEJTKuwZoUlQ6eYcLuBYFpfO4gLXEj+h0LUadFyS09+lwZ/6eTZX/1tiAwqRHjAmzRc1QCNlZZOnv8uQcgsY6TR/p6YdpxGQnKpDGIPHEDeOPO0RQcEt5XpsJ9jrvMX/qtiiZEZbDnka2lITExJcTQqQmVP7LptrC+KF7GGDI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705682393; c=relaxed/simple; bh=hRwFxaLVM/9prIFMvwSX+LskTGsLe2VRFiqmVSZ/hW0=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=i9DA8hrPkO6j8sHQ1myn8tAw64qXKwivHbNIEYbnxTcq6sZ+8juyN0540bIEFkSQr7fTHLyPrbstNecRkeTq5i22bXflZ0HdtNBUEDtluD/QbFdXSeLuBxR31ooRWqKw0TBQUzWkSY9hDERJW4p6HnUqPRtfXk1snc4IPvY7oeI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 933021042; Fri, 19 Jan 2024 08:40:35 -0800 (PST) Received: from e126817.. (e126817.cambridge.arm.com [10.2.3.5]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id C4CFD3F73F; Fri, 19 Jan 2024 08:39:46 -0800 (PST) From: Ben Gainey To: linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Cc: 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, Ben Gainey Subject: [PATCH 0/1] Support PERF_SAMPLE_READ with inherit_stat Date: Fri, 19 Jan 2024 16:39:23 +0000 Message-ID: <20240119163924.2801678-1-ben.gainey@arm.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit This change allows events to use PERF_SAMPLE READ with inherit so long as both inherit_stat and PERF_SAMPLE_TID are set. Currently it is not possible to use PERF_SAMPLE_READ with inherit. This restriction assumes the user is interested in collecting aggregate statistics as per `perf stat`. It prevents a user from collecting per-thread samples using counter groups from a multi-threaded or multi-process application, as with `perf record -e '{....}:S'`. Instead users must use system-wide mode, or forgo the ability to sample counter groups. System-wide mode is often problematic as it requires specific permissions (no CAP_PERFMON / root access), or may lead to capture of significant amounts of extra data from other processes running on the system. Perf already supports the ability to collect per-thread counts with `inherit` via the `inherit_stat` flag. This patch changes `perf_event_alloc` relaxing the restriction to combine `inherit` with `PERF_SAMPLE_READ` so that the combination will be allowed so long as `inherit_stat` and `PERF_SAMPLE_TID` are enabled. 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. This patch has been tested on aarch64 both my manual inspection of the output of `perf script -D` and through a modified version of Arm's commercial profiling tools and the numbers appear to line up as one would expect, but some further validation across other architectures and/or edge cases would be welcome. This patch was developed and tested on top of v6.7. Ben Gainey (1): perf: Support PERF_SAMPLE_READ with inherit_stat kernel/events/core.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) -- 2.43.0