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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 02C97EDEC4D for ; Wed, 13 Sep 2023 13:12:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240697AbjIMNMH (ORCPT ); Wed, 13 Sep 2023 09:12:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44444 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240962AbjIMNLy (ORCPT ); Wed, 13 Sep 2023 09:11:54 -0400 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AFF6326AA for ; Wed, 13 Sep 2023 06:11:39 -0700 (PDT) Received: from lhrpeml500005.china.huawei.com (unknown [172.18.147.206]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4Rm11t0dbbz6D99p; Wed, 13 Sep 2023 21:06:58 +0800 (CST) Received: from localhost (10.202.227.76) by lhrpeml500005.china.huawei.com (7.191.163.240) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.31; Wed, 13 Sep 2023 14:11:37 +0100 Date: Wed, 13 Sep 2023 14:11:36 +0100 From: Jonathan Cameron To: Jinhui Guo , CC: , , , , Subject: Re: [PATCH] arm64: cpufeature: Expose the real mpidr value to EL0 Message-ID: <20230913141136.00006a47@Huawei.com> In-Reply-To: <20230913105133.2902-1-guojinhui.liam@bytedance.com> References: <20230912115116.000049b0@Huawei.com> <20230913105133.2902-1-guojinhui.liam@bytedance.com> Organization: Huawei Technologies Research and Development (UK) Ltd. X-Mailer: Claws Mail 4.1.0 (GTK 3.24.33; x86_64-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.202.227.76] X-ClientProxiedBy: lhrpeml500005.china.huawei.com (7.191.163.240) To lhrpeml500005.china.huawei.com (7.191.163.240) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 13 Sep 2023 18:51:33 +0800 Jinhui Guo wrote: > > As a follow up question, is there some information that is missing from > > current topology description? (there is lots missing but I'm curious > > as to what might matter for your use case!) > > We want to know the infomation about dies to advoid memroy accessing > across dies (some settings like 2 numa per die). The NUMA access characteristics should give you the info you want - it's the variation in latency and bandwidth between dies that matters, not that they are dies. If you got really bad access characteristics across a die that info would be equally useful. I think it is not that this is a die that matters, but rather that there are groups of Numa nodes with relatively small differences in access characteristics, then others with much larger variation (and I assume a layer above that which is inter socket which is even worse). The info is in HMAT, but the kernel presentation of HMAT is rather limited currently - so you may want to look at extending what is visible in sysfs from that table. Thanks, Jonathan > > thanks, > > Jinhui Guo >