From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.10]) (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 41CE13F7874; Fri, 27 Mar 2026 17:30:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.10 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774632643; cv=none; b=Qy9nhmfDD6SjwJxWTF94CrcbS3fypO9U/ef0jmxCtPmDjBQUqi6EkoLLmAXKChe7DevYtEKMQaxpdsD+kfNLEBBmb3lK7ghFo2R9EEVbKZ4LYCPT/5UpOYjfx0MZErMEzpBCUZ/dbWCNXs2wGBU7seUsjhkw2/z/0O+Zhh07TJE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774632643; c=relaxed/simple; bh=vdVGOFggcLsLjQO8Oz6D8OHxU7nWHZuMBjavtoRryUk=; h=From:Date:To:cc:Subject:In-Reply-To:Message-ID:References: MIME-Version:Content-Type; b=D0NTC0c3n8lfmsSU7n4EJ+B0Jj5TZl08P70qIbW/iXZDqVacVN0y7mU2yGdjIxUWnBnw3DeZ3tnMJmck40q5W9AoeW87vQ3BmpiYVgjJNxMWpTwJo48vShMmjrBqSSmwZw/y5zvpJWRJvkGkqWDsUnJKNjAVyucaWLfgAbJGrbY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=RAfJeJ7/; arc=none smtp.client-ip=198.175.65.10 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="RAfJeJ7/" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1774632643; x=1806168643; h=from:date:to:cc:subject:in-reply-to:message-id: references:mime-version; bh=vdVGOFggcLsLjQO8Oz6D8OHxU7nWHZuMBjavtoRryUk=; b=RAfJeJ7/p/28znAPbcWe1IJlhCAD3VjCqLb7BMoqadtyovIjRNNB225G JK7u7SpL+wZqGvIcmhjj9QHAOOQFG09xl23jcTU2jfcL9NDvJnli/FX3c ft4tOCS7I6Uh+nE854Uu6JXmB9VV3J6tJlnq6kU+t7Uxk0WjZi4SmmYzN FoL160M0BNkxCujTo9bkdwv7FPU7GFaPcNjNcxe2kZeARP5o63liXS3e2 H4xcNCNXwKlFDuZW7qS1jIVfQxi6rvtEuZRbXJx60zxNNbtCb10HFRJKE 3ypVi8sxWkYi37vZFUAiCwmCkBAQRzFjHkA5z2eyuMzCcjHRnyepiXCOJ Q==; X-CSE-ConnectionGUID: dxsSvrWPRUeAmgiCF/oTSQ== X-CSE-MsgGUID: K9Vm7h8ARL6oA5QK3LW4FQ== X-IronPort-AV: E=McAfee;i="6800,10657,11742"; a="93096787" X-IronPort-AV: E=Sophos;i="6.23,144,1770624000"; d="scan'208";a="93096787" Received: from orviesa010.jf.intel.com ([10.64.159.150]) by orvoesa102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Mar 2026 10:30:42 -0700 X-CSE-ConnectionGUID: cWehFI2GSB+XxZQ7vRayEw== X-CSE-MsgGUID: 14DaV494Qz63ZNO+q3impQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,144,1770624000"; d="scan'208";a="224582943" Received: from ijarvine-mobl1.ger.corp.intel.com (HELO localhost) ([10.245.244.186]) by orviesa010-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Mar 2026 10:30:36 -0700 From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= Date: Fri, 27 Mar 2026 19:30:27 +0200 (EET) To: Reinette Chatre cc: shuah@kernel.org, Dave.Martin@arm.com, james.morse@arm.com, tony.luck@intel.com, babu.moger@amd.com, fenghuay@nvidia.com, peternewman@google.com, zide.chen@intel.com, dapeng1.mi@linux.intel.com, ben.horgan@arm.com, yu.c.chen@intel.com, jason.zeng@intel.com, linux-kselftest@vger.kernel.org, LKML , patches@lists.linux.dev Subject: Re: [PATCH v3 06/10] selftests/resctrl: Increase size of buffer used in MBM and MBA tests In-Reply-To: <32e610855f87010cd37ccc18c5eb23a1117fbb41.1773432891.git.reinette.chatre@intel.com> Message-ID: <3416b137-c79c-447a-3271-c576e8491082@linux.intel.com> References: <32e610855f87010cd37ccc18c5eb23a1117fbb41.1773432891.git.reinette.chatre@intel.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="8323328-176699374-1774632627=:1037" This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323328-176699374-1774632627=:1037 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: QUOTED-PRINTABLE On Fri, 13 Mar 2026, Reinette Chatre wrote: > Errata for Sierra Forest [1] (SRF42) and Granite Rapids [2] (GNR12) > describe the problem that MBM on Intel RDT may overcount memory bandwidth > measurements. The resctrl tests compare memory bandwidth reported by iMC > PMU to that reported by MBM causing the tests to fail on these systems > depending on the settings of the platform related to the errata. >=20 > Since the resctrl tests need to run under various conditions it is not > possible to ensure system settings are such that MBM will not overcount. > It has been observed that the overcounting can be controlled via the > buffer size used in the MBM and MBA tests that rely on comparisons > between iMC PMU and MBM measurements. >=20 > Running the MBM test on affected platforms with different buffer sizes it > can be observed that the difference between iMC PMU and MBM counts reduce > as the buffer size increases. After increasing the buffer size to more > than 4X the differences between iMC PMU and MBM become insignificant. >=20 > Increase the buffer size used in MBM and MBA tests to 4X L3 size to reduc= e > possibility of tests failing due to difference in counts reported by iMC > PMU and MBM. >=20 > Signed-off-by: Reinette Chatre > Tested-by: Chen Yu > Link: https://edc.intel.com/content/www/us/en/design/products-and-solutio= ns/processors-and-chipsets/sierra-forest/xeon-6700-series-processor-with-e-= cores-specification-update/errata-details/ # [1] > Link: https://edc.intel.com/content/www/us/en/design/products-and-solutio= ns/processors-and-chipsets/birch-stream/xeon-6900-6700-6500-series-processo= rs-with-p-cores-specification-update/011US/errata-details/ # [2] > --- > Changes since v2: > - Add Chen Yu's tag. > --- > tools/testing/selftests/resctrl/fill_buf.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) >=20 > diff --git a/tools/testing/selftests/resctrl/fill_buf.c b/tools/testing/s= elftests/resctrl/fill_buf.c > index 19a01a52dc1a..b9fa7968cd6e 100644 > --- a/tools/testing/selftests/resctrl/fill_buf.c > +++ b/tools/testing/selftests/resctrl/fill_buf.c > @@ -139,6 +139,6 @@ ssize_t get_fill_buf_size(int cpu_no, const char *cac= he_type) > =09if (ret) > =09=09return ret; > =20 > -=09return cache_total_size * 2 > MINIMUM_SPAN ? > -=09=09=09cache_total_size * 2 : MINIMUM_SPAN; > +=09return cache_total_size * 4 > MINIMUM_SPAN ? > +=09=09=09cache_total_size * 4 : MINIMUM_SPAN; > } >=20 Reviewed-by: Ilpo J=E4rvinen --=20 i. --8323328-176699374-1774632627=:1037--