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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 14175C43387 for ; Wed, 19 Dec 2018 00:26:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DE89721852 for ; Wed, 19 Dec 2018 00:26:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727595AbeLSA0d (ORCPT ); Tue, 18 Dec 2018 19:26:33 -0500 Received: from mga11.intel.com ([192.55.52.93]:26170 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726785AbeLSA0d (ORCPT ); Tue, 18 Dec 2018 19:26:33 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 18 Dec 2018 16:26:32 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,370,1539673200"; d="scan'208";a="119934500" Received: from cli6-desk1.ccr.corp.intel.com (HELO [10.239.161.118]) ([10.239.161.118]) by orsmga001.jf.intel.com with ESMTP; 18 Dec 2018 16:26:30 -0800 Subject: Re: [PATCH v6 1/3] x86/fpu: track AVX-512 usage of tasks To: Andi Kleen Cc: Thomas Gleixner , Aubrey Li , mingo@redhat.com, peterz@infradead.org, hpa@zytor.com, tim.c.chen@linux.intel.com, dave.hansen@intel.com, arjan@linux.intel.com, linux-kernel@vger.kernel.org References: <20181218042218.8653-1-aubrey.li@intel.com> <62997df2-0817-b54d-b11e-00a567f1d67c@linux.intel.com> <20181218213826.GI25620@tassilo.jf.intel.com> From: "Li, Aubrey" Message-ID: <6695cf98-17e8-df5f-4dac-264435e2aea5@linux.intel.com> Date: Wed, 19 Dec 2018 08:26:30 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 MIME-Version: 1.0 In-Reply-To: <20181218213826.GI25620@tassilo.jf.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/12/19 5:38, Andi Kleen wrote: >> I misunderstood, you mean 32bit kernel, not 32bit machine. Theoretically 32bit >> kernel can use AVX512, but not sure if anyone use it like this. get_jiffies_64() >> includes jiffies_lock ops so not good in context switch. So I want to use raw >> jiffies_64 here. jiffies is a good candidate but it has wraparound overflow issue. >> Other time source are expensive here. >> >> Should I limit the code only running on 64bit kernel? > > Yes making it 64bit only should be fine. > > Other alternative would be to use 32bit jiffies on 32bit. I assume > wrapping is not that big a problem here. > Thomas, is this acceptable? Thanks, -Aubrey