From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.126]) (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 77C31320E for ; Thu, 28 Sep 2023 19:14:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1695928446; x=1727464446; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=mn6nYHQ+REP1+buEIYzgvASYIMVA5gLIDjoJUxkB0Ok=; b=duWY74iPCS0aoa5n5Gjw2tawpKPLUFeu/NI0PYnZv6O8k4rxd0uWWOX/ PK7cKYgAWHc0XCTkgg/J4D0ezok4af01egNJRsDdcCUxNf/MJbWBJ3MyP afgLnuek101P3i38jS9+D+a8XCFtxLIsPCczd6HFrzMkw9+7kUbfZZH0L ZQQB6jq0b8CwfAR1RjeyHNKewWZfLdT4ezf1FOuKCbZUTps6k8gTLeaNi s5fVOX9eJb4qN87kpYXHrL1pWYExBeSH6rnaR7KxyuOT+ieJ8DMbSLWX8 8X8n/hQLkF6FlRRhEWZuZ3PJjqwt4dJyGVlDtX7jm3EqE3CA3ACBYA3VY g==; X-IronPort-AV: E=McAfee;i="6600,9927,10847"; a="367213959" X-IronPort-AV: E=Sophos;i="6.03,185,1694761200"; d="scan'208";a="367213959" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Sep 2023 12:14:02 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10847"; a="779020047" X-IronPort-AV: E=Sophos;i="6.03,185,1694761200"; d="scan'208";a="779020047" Received: from agluck-desk3.sc.intel.com ([172.25.222.74]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Sep 2023 12:14:01 -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 v6 8/8] x86/resctrl: Update documentation with Sub-NUMA cluster changes Date: Thu, 28 Sep 2023 12:13:49 -0700 Message-ID: <20230928191350.205703-9-tony.luck@intel.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230928191350.205703-1-tony.luck@intel.com> References: <20230829234426.64421-1-tony.luck@intel.com> <20230928191350.205703-1-tony.luck@intel.com> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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. Signed-off-by: Tony Luck --- Changes since v5: Added addtional details about challenges tracking tasks when SNC mode is enabled. --- Documentation/arch/x86/resctrl.rst | 34 +++++++++++++++++++++++++++--- 1 file changed, 31 insertions(+), 3 deletions(-) diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst index cb05d90111b4..d6b6a4cfd967 100644 --- a/Documentation/arch/x86/resctrl.rst +++ b/Documentation/arch/x86/resctrl.rst @@ -345,9 +345,15 @@ When control is enabled all CTRL_MON groups will also contain: When monitoring is enabled all MON groups will also contain: "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. E.g. on a system with + SNC mode disabled with two L3 domains there will be subdirectories + "mon_L3_00" and "mon_L3_01". The numerical suffix refers to the + L3 cache id. With SNC enabled the directory names are the same, + but the numerical suffix refers to the node id. + Mappings from node ids to CPUs are available in the + /sys/devices/system/node/node*/cpulist files. 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 @@ -452,6 +458,28 @@ and 0xA are not. On a system with 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. +Notes on Sub-NUMA Cluster mode +============================== +When SNC mode is enabled the "llc_occupancy", "mbm_total_bytes", and +"mbm_local_bytes" will only give meaningful results for well behaved NUMA +applications. I.e. those that perform the majority of memory accesses +to memory on the local NUMA node to the CPU where the task is executing. +Note that Linux may load balance tasks between Sub-NUMA nodes much +more readily than between regular NUMA nodes since the CPUs on SNC +share the same L3 cache and the system may report the NUMA distance +between SNC nodes with a lower value than used for regular NUMA nodes. +Tasks that migrate between nodes will have their traffic recorded by the +counters in different SNC nodes so a user will need to read mon_data +files from each node on which the task executed to get the full +view of traffic for which the task was 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 ========================================== -- 2.41.0