From nobody Wed Dec 17 02:38:57 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E0886C0032E for ; Fri, 20 Oct 2023 21:32:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345191AbjJTVcR (ORCPT ); Fri, 20 Oct 2023 17:32:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58014 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232860AbjJTVcB (ORCPT ); Fri, 20 Oct 2023 17:32:01 -0400 Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.126]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C9454D7D; Fri, 20 Oct 2023 14:31:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1697837507; x=1729373507; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=XsD7RMOBK+QP/Vh09NEqgiBSp4V/6/e9uwNicno2Kjw=; b=kU6YjZcXpP8F0fp+Rn5rVeGavxa5AiL9S2aKQwDCqzHXRAcgQ71E4lgV 4xXLawbQJ8IsfZG/KzX9Bu94w+inVcjIXjGVrsYTpzwCgfbN2kLsCK3OE SNfwIZCM9KPg7F3rhY/vl/r92FsVxsNGxUr8D6bEcsoUQVIGDl2x1xsB6 kYhC6tvhJyoeTEPXNDBXuQhgg5853v01Ne7e771LKu/Xb4fyoSchlsKQ5 ohQhC1aipK2igmn9xW2vyug4YlVKidgDfjUkHp1YOlDngzQgDsaX+ICyL KanvFsm3h4/YwinY8JVkkmOdpE7EOErDi3S+PcttBVeymnA32hx6SZXrH g==; X-IronPort-AV: E=McAfee;i="6600,9927,10869"; a="371647201" X-IronPort-AV: E=Sophos;i="6.03,239,1694761200"; d="scan'208";a="371647201" Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Oct 2023 14:31:13 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10869"; a="881184553" X-IronPort-AV: E=Sophos;i="6.03,239,1694761200"; d="scan'208";a="881184553" Received: from agluck-desk3.sc.intel.com ([172.25.222.74]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Oct 2023 14:31:12 -0700 From: Tony Luck To: Fenghua Yu , Reinette Chatre , Peter Newman , Jonathan Corbet , Shuah Khan , x86@kernel.org Cc: Shaopeng Tan , James Morse , Jamie Iles , Babu Moger , Randy Dunlap , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, patches@lists.linux.dev, Tony Luck Subject: [PATCH v9 8/8] x86/resctrl: Update documentation with Sub-NUMA cluster changes Date: Fri, 20 Oct 2023 14:31:00 -0700 Message-ID: <20231020213100.123598-9-tony.luck@intel.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20231020213100.123598-1-tony.luck@intel.com> References: <20231003213043.13565-1-tony.luck@intel.com> <20231020213100.123598-1-tony.luck@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" With Sub-NUMA Cluster mode enabled the scope of monitoring resources is per-NODE instead of per-L3 cache. Suffixes of directories with "L3" in their name refer to Sub-NUMA nodes instead of L3 cache ids. Users should be aware that SNC mode also affects the amount of L3 cache available for allocation within each SNC node. Reviewed-by: Peter Newman Signed-off-by: Tony Luck --- Changes since v6: Added Peter's review tag Documentation/arch/x86/resctrl.rst | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-) diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/re= sctrl.rst index a6279df64a9d..d1db200db5f9 100644 --- a/Documentation/arch/x86/resctrl.rst +++ b/Documentation/arch/x86/resctrl.rst @@ -366,9 +366,9 @@ When control is enabled all CTRL_MON groups will also c= ontain: When monitoring is enabled all MON groups will also contain: =20 "mon_data": - This contains a set of files organized by L3 domain and by - RDT event. E.g. on a system with two L3 domains there will - be subdirectories "mon_L3_00" and "mon_L3_01". Each of these + This contains a set of files organized by L3 domain or by NUMA + node (depending on whether Sub-NUMA Cluster (SNC) mode is disabled + or enabled respectively) and by RDT event. Each of these directories have one file per event (e.g. "llc_occupancy", "mbm_total_bytes", and "mbm_local_bytes"). In a MON group these files provide a read out of the current value of the event for @@ -478,6 +478,23 @@ if non-contiguous 1s value is supported. On a system w= ith a 20-bit mask each bit represents 5% of the capacity of the cache. You could partition the cache into four equal parts with masks: 0x1f, 0x3e0, 0x7c00, 0xf8000. =20 +Notes on Sub-NUMA Cluster mode +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D +When SNC mode is enabled Linux may load balance tasks between Sub-NUMA +nodes much more readily than between regular NUMA nodes since the CPUs +on Sub-NUMA nodes share the same L3 cache and the system may report +the NUMA distance between Sub-NUMA nodes with a lower value than used +for regular NUMA nodes. Users who do not bind tasks to the CPUs of a +specific Sub-NUMA node must read the "llc_occupancy", "mbm_total_bytes", +and "mbm_local_bytes" for all Sub-NUMA nodes where the tasks may execute +to get the full view of traffic for which the tasks were the source. + +The cache allocation feature still provides the same number of +bits in a mask to control allocation into the L3 cache. But each +of those ways has its capacity reduced because the cache is divided +between the SNC nodes. The values reported in the resctrl +"size" files are adjusted accordingly. + Memory bandwidth Allocation and monitoring =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =20 --=20 2.41.0