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 8B9DDC54EE9 for ; Thu, 22 Sep 2022 03:47:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229720AbiIVDrw (ORCPT ); Wed, 21 Sep 2022 23:47:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58606 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229519AbiIVDrr (ORCPT ); Wed, 21 Sep 2022 23:47:47 -0400 Received: from out30-43.freemail.mail.aliyun.com (out30-43.freemail.mail.aliyun.com [115.124.30.43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1C027AB188 for ; Wed, 21 Sep 2022 20:47:45 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R181e4;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=9;SR=0;TI=SMTPD_---0VQQi8tk_1663818461; Received: from 30.240.98.118(mailfrom:xhao@linux.alibaba.com fp:SMTPD_---0VQQi8tk_1663818461) by smtp.aliyun-inc.com; Thu, 22 Sep 2022 11:47:42 +0800 Message-ID: <4117f7f5-8156-d8c7-9e48-55a1b632f83d@linux.alibaba.com> Date: Thu, 22 Sep 2022 11:47:41 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Subject: Re: [RFC 0/6] migrate_pages(): batch TLB flushing To: Zi Yan , Huang Ying Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Yang Shi , Baolin Wang , Oscar Salvador , Matthew Wilcox References: <20220921060616.73086-1-ying.huang@intel.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 Hi Huang,     This is an exciting change, but on ARM64 machine the TLB flushing are not through IPI, it depends on 'vale1is' instruction，so I'm wondering if there's also a  benefit on arm64, and I'm going to test it on an ARM64 machine. 在 2022/9/21 下午11:47, Zi Yan 写道: > On 21 Sep 2022, at 2:06, Huang Ying wrote: > >> From: "Huang, Ying" >> >> Now, migrate_pages() migrate pages one by one, like the fake code as >> follows, >> >> for each page >> unmap >> flush TLB >> copy >> restore map >> >> If multiple pages are passed to migrate_pages(), there are >> opportunities to batch the TLB flushing and copying. That is, we can >> change the code to something as follows, >> >> for each page >> unmap >> for each page >> flush TLB >> for each page >> copy >> for each page >> restore map >> >> The total number of TLB flushing IPI can be reduced considerably. And >> we may use some hardware accelerator such as DSA to accelerate the >> page copying. >> >> So in this patch, we refactor the migrate_pages() implementation and >> implement the TLB flushing batching. Base on this, hardware >> accelerated page copying can be implemented. >> >> If too many pages are passed to migrate_pages(), in the naive batched >> implementation, we may unmap too many pages at the same time. The >> possibility for a task to wait for the migrated pages to be mapped >> again increases. So the latency may be hurt. To deal with this >> issue, the max number of pages be unmapped in batch is restricted to >> no more than HPAGE_PMD_NR. That is, the influence is at the same >> level of THP migration. >> >> We use the following test to measure the performance impact of the >> patchset, >> >> On a 2-socket Intel server, >> >> - Run pmbench memory accessing benchmark >> >> - Run `migratepages` to migrate pages of pmbench between node 0 and >> node 1 back and forth. >> >> With the patch, the TLB flushing IPI reduces 99.1% during the test and >> the number of pages migrated successfully per second increases 291.7%. > Thank you for the patchset. Batching page migration will definitely > improve its throughput from my past experiments[1] and starting with > TLB flushing is a good first step. > > BTW, what is the rationality behind the increased page migration > success rate per second? > >> This patchset is based on v6.0-rc5 and the following patchset, >> >> [PATCH -V3 0/8] migrate_pages(): fix several bugs in error path >> https://lore.kernel.org/lkml/20220817081408.513338-1-ying.huang@intel.com/ >> >> The migrate_pages() related code is converting to folio now. So this >> patchset cannot apply recent akpm/mm-unstable branch. This patchset >> is used to check the basic idea. If it is OK, I will rebase the >> patchset on top of folio changes. >> >> Best Regards, >> Huang, Ying > > [1] https://lwn.net/Articles/784925/ > > -- > Best Regards, > Yan, Zi