From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5C191C4360F for ; Thu, 21 Feb 2019 01:18:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2E96D2089F for ; Thu, 21 Feb 2019 01:18:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726845AbfBUBSH (ORCPT ); Wed, 20 Feb 2019 20:18:07 -0500 Received: from mga14.intel.com ([192.55.52.115]:44834 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725875AbfBUBSF (ORCPT ); Wed, 20 Feb 2019 20:18:05 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 20 Feb 2019 17:18:05 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,393,1544515200"; d="scan'208";a="126016849" Received: from aubrey-skl.sh.intel.com ([10.239.53.19]) by fmsmga008.fm.intel.com with ESMTP; 20 Feb 2019 17:18:03 -0800 From: Aubrey Li To: tglx@linutronix.de, mingo@redhat.com, peterz@infradead.org, hpa@zytor.com Cc: ak@linux.intel.com, tim.c.chen@linux.intel.com, dave.hansen@intel.com, arjan@linux.intel.com, aubrey.li@intel.com, linux-kernel@vger.kernel.org, Aubrey Li Subject: [PATCH v12 3/3] Documentation/filesystems/proc.txt: add AVX512_elapsed_ms Date: Thu, 21 Feb 2019 09:17:41 +0800 Message-Id: <20190221011741.97070-3-aubrey.li@linux.intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190221011741.97070-1-aubrey.li@linux.intel.com> References: <20190221011741.97070-1-aubrey.li@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Added AVX512_elapsed_ms in /proc//status. Report it in Documentation/filesystems/proc.txt Signed-off-by: Aubrey Li Cc: Peter Zijlstra Cc: Andi Kleen Cc: Tim Chen Cc: Dave Hansen Cc: Arjan van de Ven --- Documentation/filesystems/proc.txt | 28 +++++++++++++++++++++++++++- 1 file changed, 27 insertions(+), 1 deletion(-) diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index 66cad5c86171..425f2f09c9aa 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -45,6 +45,7 @@ Table of Contents 3.9 /proc//map_files - Information about memory mapped files 3.10 /proc//timerslack_ns - Task timerslack value 3.11 /proc//patch_state - Livepatch patch operation state + 3.12 /proc//AVX512_elapsed_ms - time elapsed since last AVX512 use 4 Configuring procfs 4.1 Mount options @@ -207,6 +208,7 @@ read the file /proc/PID/status: Speculation_Store_Bypass: thread vulnerable voluntary_ctxt_switches: 0 nonvoluntary_ctxt_switches: 1 + AVX512_elapsed_ms: 8 This shows you nearly the same information you would get if you viewed it with the ps command. In fact, ps uses the proc file system to obtain its @@ -224,7 +226,7 @@ asynchronous manner and the value may not be very precise. To see a precise snapshot of a moment, you can see /proc//smaps file and scan page table. It's slow but very precise. -Table 1-2: Contents of the status files (as of 4.19) +Table 1-2: Contents of the status files (as of 5.1) .............................................................................. Field Content Name filename of the executable @@ -289,6 +291,7 @@ Table 1-2: Contents of the status files (as of 4.19) Mems_allowed_list Same as previous, but in "list format" voluntary_ctxt_switches number of voluntary context switches nonvoluntary_ctxt_switches number of non voluntary context switches + AVX512_elapsed_ms time elapsed since last AVX512 use in millisecond .............................................................................. Table 1-3: Contents of the statm files (as of 2.6.8-rc3) @@ -1948,6 +1951,29 @@ patched. If the patch is being enabled, then the task has already been patched. If the patch is being disabled, then the task hasn't been unpatched yet. +3.12 /proc//AVX512_elapsed_ms - time elapsed since last AVX512 use +-------------------------------------------------------------------------- +If AVX512 is supported on the machine, this file displays time elapsed since +last AVX512 usage of the task in millisecond. + +The per-task AVX512 usage tracking mechanism is added during context switch. +When the task is scheduled out, the AVX512 timestamp of the task is tagged +by jiffies if AVX512 usage is detected. + +When this interface is queried, AVX512_elapsed_ms is calculated as follows: + + delta = (long)(jiffies_now - AVX512_timestamp); + AVX512_elpased_ms = jiffies_to_msecs(delta); + +Because this tracking mechanism depends on context switch, the number of +AVX512_elapsed_ms could be inaccurate if the AVX512 using task runs alone on +a CPU and not scheduled out for a long time. An extreme experiment shows a +task is spinning on the AVX512 ops on an isolated CPU, but the longest elapsed +time is close to 4 seconds(HZ = 250). + +So 5s or even longer is an appropriate threshold for the job scheduler to poll +and decide if the task should be classifed as an AVX512 task and migrated +away from the core on which a Non-AVX512 task is running. ------------------------------------------------------------------------------ Configuring procfs -- 2.17.1