From nobody Mon Jun 29 15:59:42 2026 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 9B588C433F5 for ; Mon, 7 Feb 2022 18:24:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237301AbiBGSYI (ORCPT ); Mon, 7 Feb 2022 13:24:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49936 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233874AbiBGSW7 (ORCPT ); Mon, 7 Feb 2022 13:22:59 -0500 X-Greylist: delayed 62 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Mon, 07 Feb 2022 10:22:58 PST Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 690E6C0401D9; Mon, 7 Feb 2022 10:22:58 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1644258178; x=1675794178; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=dRTBkaUrzeD1DWEd0reaqgGuCktQnIy1njrTvO0/m60=; b=bY66ZF4rK49Si7t2qd0nxaEIwbOSlO1sG58szVWqUY/GSseXuQ1dfjLL zQ/6fbSdoqwgeQllELwRb5twif3H8tFzOM8db0JMH2IG2utMhSJJwl5K/ URqv7yzyP4ieJnKvAU76OePxHDPZWiRwTtcYimNt7Hgl65MOYg2DF1hEh ExUo01ltvZ0whE3UNL52ldOWe0RfGfykv3UjO3vtQADLe4yjYKAci2mjC K9CLRsFxuRrRL+6w5XtRxKevm80tJJc5RyNkVvRDD3DanVrab2uvyecbB MbNyP8AtVFDtjsOBjg6VUYGWryfARHzFtGbYcKMGj9nx+D3dx3B40yNKj w==; X-IronPort-AV: E=McAfee;i="6200,9189,10250"; a="246368480" X-IronPort-AV: E=Sophos;i="5.88,350,1635231600"; d="scan'208";a="246368480" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Feb 2022 10:21:43 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.88,350,1635231600"; d="scan'208";a="540217904" Received: from spandruv-desk.jf.intel.com ([10.54.75.8]) by orsmga008.jf.intel.com with ESMTP; 07 Feb 2022 10:21:42 -0800 From: Srinivas Pandruvada To: corbet@lwn.net, rafael@kernel.org, hdegoede@redhat.com, markgross@kernel.org Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Srinivas Pandruvada Subject: [PATCH] Documentation: admin-guide: pm: Document uncore frequency scaling Date: Mon, 7 Feb 2022 10:21:34 -0800 Message-Id: <20220207182134.2900362-1-srinivas.pandruvada@linux.intel.com> X-Mailer: git-send-email 2.31.1 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" Added documentation to configure uncore frequency limits in Intel Xeon processors. Signed-off-by: Srinivas Pandruvada --- .../pm/intel_uncore_frequency_scaling.rst | 56 +++++++++++++++++++ .../admin-guide/pm/working-state.rst | 1 + 2 files changed, 57 insertions(+) create mode 100644 Documentation/admin-guide/pm/intel_uncore_frequency_sca= ling.rst diff --git a/Documentation/admin-guide/pm/intel_uncore_frequency_scaling.rs= t b/Documentation/admin-guide/pm/intel_uncore_frequency_scaling.rst new file mode 100644 index 000000000000..b3519560594b --- /dev/null +++ b/Documentation/admin-guide/pm/intel_uncore_frequency_scaling.rst @@ -0,0 +1,56 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: + +=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 +Intel Uncore Frequency Scaling +=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 + +:Copyright: |copy| 2022 Intel Corporation + +:Author: Srinivas Pandruvada + +Introduction +=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=3D + +Uncore can consume significant amount of power in Intel's Xeon servers bas= ed +on the workload characteristics. To optimize total power and improve overa= ll +performance, SoC has an internal algorithm for scaling uncore frequency. T= hese +algorithms monitor workload usage of uncore and set a desirable frequency. + +It is possible that users have different expectations of uncore performanc= e and +want to have control over it. The objective is similar to set scaling min/= max +frequencies using cpufreq sysfs to improve compute performance. Users may = have +some latency sensitive workload where they do not want any change to uncore +frequency. Also, users may have workload which requires different core and +uncore performance at distinct phases and they want to use both cpufreq and +uncore scaling interface to distribute power and improve overall performan= ce. + +To control uncore frequency, a sysfs interface is provided in the director= y: +`/sys/devices/system/cpu/intel_uncore_frequency/`. + +There is one directory for each package and die combination as the scope of +uncore scaling control is per die in multiple dies/package SoC or per +package for single die per package SoC. The name represents the +scope of control. For example: 'package_00_die_00' is for package id 0 and +die 0 in it. + +Each package_*_die_* contains following attributes: + +``initial_max_freq_khz`` + Out of reset, this attribute represent the maximum possible frequency. + This is a read only attribute. If users adjust max_freq_khz, + they can always go back to maximum using the value from this attribute. + +``initial_min_freq_khz`` + Out of reset, this attribute represent the minimum possible frequency. + This is a read only attribute. If users adjust min_freq_khz, + they can always go back to minimum using the value from this attribute. + +``max_freq_khz`` + This attribute is used to set the maximum uncore frequency. + +``min_freq_khz`` + This attribute is used to set the minimum uncore frequency. + +``current_freq_khz`` + This attribute is used to get the current uncore frequency. diff --git a/Documentation/admin-guide/pm/working-state.rst b/Documentation= /admin-guide/pm/working-state.rst index 5d2757e2de65..ee45887811ff 100644 --- a/Documentation/admin-guide/pm/working-state.rst +++ b/Documentation/admin-guide/pm/working-state.rst @@ -15,3 +15,4 @@ Working-State Power Management cpufreq_drivers intel_epb intel-speed-select + intel_uncore_frequency_scaling --=20 2.34.1