From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D360D489FDE for ; Wed, 30 Sep 2026 23:24:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790810655; cv=none; b=RYheFBIoJytVOLKHSqVvsVO/oBcqdtvfFkJFLvWZB9tqiLM1xkmv5/BHrdwe8D0h7rzIlWOc73JlvCLdCtgfT8yPyhFcg6CX0kx2tPnfN+V/qp2xmsRd77b66/sA0pshoxBv1uIbmzXkRUjpE5RmklRb3qUDsx6LPFYQKuT7/vI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790810655; c=relaxed/simple; bh=ODKJZxCzpgbYTIaC6syrxJvyYKVUHpHckU3/O3kuKnI=; h=From:Subject:To:Cc:In-Reply-To:References:Content-Type:Date: Message-Id; b=qLANSpoFtkFToH70RYVefmuj6PSq6AGonZ4p8cILetyFesmURf8RG9JwejZ3OS5AK9GkoGmIUjLPl6VhHoQ3bjGmQ6LoipjWjM2xGHJI2mTK2waHdfJ9zRh4+H6Pwr94sdGL+K3lirTt+8BA7wchbMmmwgSkP2N0VIw1nxQzO88= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lKkTTz0g; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="lKkTTz0g" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D170C1F000FF; Wed, 30 Sep 2026 23:24:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790810648; bh=3V9IdHg7Z8pzSZ5KhwwzoaX8X8YqC1gV9bWYg1Rt0ys=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=lKkTTz0gOEKp73++mBfLiBXXeRMmcQr1cuCNSPv/dONbvMXvaAqP4P5IGmkmr9L+a Kpt60N7vF8qU1OQbrjCeQPP/PgrpPVpN9o4L1EdjUjXYj0sdyqyMFZUmebmFuvU4bI pk5jkrWYXYAIfYQ8I+Kpl3h78vw5VjlMnU9zbHnLNMGFNwe9nPdvL4Blqmg5h8PCkK JIrDL0fynYFO5K0nM82ULcSiNkRvA3FodANS25b//jFjv7UkZBflQHMj9cp8/LpSb7 OZexirQuht8BrZZoPeRvzWnS4qImeh3cWw+kGoxoMEoW9lAl6KloPLwe0yHRPI8S9N PCizpjpSV2dFg== From: sashiko-bot@kernel.org Subject: Re: [PATCH v2 2/2] perf/arm-cmn: Allow userspace to select the PMU's CPU Reply-To: sashiko-reviews@lists.linux.dev To: "Haris Okanovic" Cc: linux-perf-users@vger.kernel.org In-Reply-To: <20260930231127.3094040-3-harisokn@amazon.com> References: <20260930231127.3094040-1-harisokn@amazon.com> <20260930231127.3094040-3-harisokn@amazon.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Wed, 30 Sep 2026 23:24:07 +0000 Message-Id: <20260930232407.D170C1F000FF@smtp.kernel.org> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: > arm_cmn_probe() picks the CPU that owns the PMU with >=20 > cmn->cpu =3D cpumask_local_spread(0, dev_to_node(cmn->dev)); >=20 > and arm_cmn_event_init() then binds every event to it unconditionally. > That choice is only revisited by the CPU hotplug callbacks, so in > practice the PMU stays on the first CPU local to the interconnect's NUMA > node, which is usually CPU 0. >=20 > All of the PMU's recurring work therefore lands on one CPU. This is > problematic on systems which reserve particular CPUs for latency > sensitive work or confine background activity to a chosen set of > housekeeping CPUs. >=20 > There is no way to set it explicitly. perf_event_open() and 'perf stat > [ ... ] > The attribute expresses a preference rather than a guarantee. The > hotplug callbacks may still move the PMU, for example when the chosen > CPU is offlined. >=20 > Signed-off-by: Haris Okanovic Sashiko has reviewed this patch and found no issues. It looks great! --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20260930231127.3094= 040-1-harisokn@amazon.com?part=3D2