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[23.128.96.18]) by mx.google.com with ESMTP id w13si2526401ejo.365.2021.04.15.10.03.33; Thu, 15 Apr 2021 10:04:02 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234155AbhDORA4 (ORCPT + 99 others); Thu, 15 Apr 2021 13:00:56 -0400 Received: from mga12.intel.com ([192.55.52.136]:34921 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233343AbhDORAv (ORCPT ); Thu, 15 Apr 2021 13:00:51 -0400 IronPort-SDR: OHhhgSvL1knVaffF5+9Y9jqjDS0e6wq6a8EPoqb7+/zfnAFCNVYbIiKRMVnA4HrcGn996pT1fD PBp/1vCGpQOQ== X-IronPort-AV: E=McAfee;i="6200,9189,9955"; a="174388996" X-IronPort-AV: E=Sophos;i="5.82,225,1613462400"; d="scan'208";a="174388996" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Apr 2021 10:00:26 -0700 IronPort-SDR: hgUzngCn86j/c2pqpcrkj6Lz0JNLv2+t8IDvvVYVYLhkvO/MBQZKqpxUGsl11DN+sl9hOoRKyF cex47C4xHkQA== X-IronPort-AV: E=Sophos;i="5.82,225,1613462400"; d="scan'208";a="452998138" Received: from juanfer-mobl.amr.corp.intel.com (HELO [10.252.130.182]) ([10.252.130.182]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Apr 2021 10:00:25 -0700 Subject: Re: Candidate Linux ABI for Intel AMX and hypothetical new related features To: Andy Lutomirski , Len Brown Cc: Willy Tarreau , Florian Weimer , "Bae, Chang Seok" , X86 ML , LKML , linux-abi@vger.kernel.org, "libc-alpha@sourceware.org" , Rich Felker , Kyle Huey , Keno Fischer References: <87lf9nk2ku.fsf@oldenburg.str.redhat.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/15/21 9:24 AM, Andy Lutomirski wrote: > In the patches, *as submitted*, if you trip the XFD #NM *once* and you > are the only thread on the system to do so, you will eat the cost of a > WRMSR on every subsequent context switch. I think you're saying: If a thread trips XFD #NM *once*, every switch to and from *that* thread will incur the WRMSR cost. The first time I read this, I thought you were saying that all threads would incur a WRMSR cost on every context switch. If that's the case, I grossly misread the patches. :)