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 76C69C19F2B for ; Thu, 4 Aug 2022 09:31:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239221AbiHDJam (ORCPT ); Thu, 4 Aug 2022 05:30:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52616 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239139AbiHDJaj (ORCPT ); Thu, 4 Aug 2022 05:30:39 -0400 Received: from out30-132.freemail.mail.aliyun.com (out30-132.freemail.mail.aliyun.com [115.124.30.132]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6F1753DF39 for ; Thu, 4 Aug 2022 02:30:38 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R811e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045192;MF=xhao@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0VLMBxaE_1659605434; Received: from 30.240.99.20(mailfrom:xhao@linux.alibaba.com fp:SMTPD_---0VLMBxaE_1659605434) by smtp.aliyun-inc.com; Thu, 04 Aug 2022 17:30:35 +0800 Message-ID: Date: Thu, 4 Aug 2022 17:30:33 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.0.3 Subject: Re: [RFC PATCH V4 1/1] mm: add last level page table numa info to /proc/pid/numa_pgtable To: David Hildenbrand , willy@infradead.org Cc: akpm@linux-foundation.org, adobriyan@gmail.com, keescook@chromium.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20220801121727.76186-1-xhao@linux.alibaba.com> <20220801121727.76186-2-xhao@linux.alibaba.com> <0c1f9e76-9b1d-7069-bb09-c18e4f19f0c4@redhat.com> From: haoxin In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2022/8/4 下午4:12, David Hildenbrand 写道: > On 04.08.22 10:04, haoxin wrote: >> 在 2022/8/1 下午9:28, David Hildenbrand 写道: >>> On 01.08.22 14:17, Xin Hao wrote: >>>> In many data center servers, the shared memory architectures is >>>> Non-Uniform Memory Access (NUMA), remote numa node data access >>>> often brings a high latency problem, but what we are easy to ignore >>>> is that the page table remote numa access, It can also leads to a >>>> performance degradation. >>> Let me try rewriting: >>> >>> " >>> Many data center servers employ Non-Uniform Memory Access (NUMA) >>> architectures. Remote numa memory access results in high latency. While >>> memory placement is one issue, sub-optimal page table placement can also >>> result in surprise performance degradation. >>> " >> Thanks,  it reads more clearly. >> >>>> So there add a new interface in /proc, This will help developers to >>>> get more info about performance issues if they are caused by cross-NUMA. >>> Why do we only care about "last level page table", why not about the others? >>> >>> IMHO, we could emit something like "0, 1, 3, 0" instead for a given user >>> space address, showing the NUMA node the page table belongs to from >>> highest to lowest page table level. >> I have planned to implement the PTE page table in this version first, >> and then support other page tables in the next patch later. > If there are plans, let's do it all at once, to get a good and single > interface to expose that information. Ok, thanks for your suggestion, I will implement it in the next version. >