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 A6ECDC4167D for ; Mon, 13 Nov 2023 12:59:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230012AbjKMM7d (ORCPT ); Mon, 13 Nov 2023 07:59:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50152 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229511AbjKMM7c (ORCPT ); Mon, 13 Nov 2023 07:59:32 -0500 Received: from out30-111.freemail.mail.aliyun.com (out30-111.freemail.mail.aliyun.com [115.124.30.111]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CBA03D7E for ; Mon, 13 Nov 2023 04:59:28 -0800 (PST) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R111e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046056;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---0VwL8Mwl_1699880365; Received: from 30.97.48.50(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0VwL8Mwl_1699880365) by smtp.aliyun-inc.com; Mon, 13 Nov 2023 20:59:26 +0800 Message-ID: <517f2a75-638d-4f17-a5c1-719e15507c6a@linux.alibaba.com> Date: Mon, 13 Nov 2023 20:59:37 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH] mm: support large folio numa balancing To: David Hildenbrand , akpm@linux-foundation.org Cc: ying.huang@intel.com, wangkefeng.wang@huawei.com, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, John Hubbard References: <606d2d7a-d937-4ffe-a6f2-dfe3ae5a0c91@redhat.com> From: Baolin Wang In-Reply-To: <606d2d7a-d937-4ffe-a6f2-dfe3ae5a0c91@redhat.com> 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 On 11/13/2023 6:53 PM, David Hildenbrand wrote: > On 13.11.23 11:45, Baolin Wang wrote: >> Currently, the file pages already support large folio, and supporting for >> anonymous pages is also under discussion[1]. Moreover, the numa balancing >> code are converted to use a folio by previous thread[2], and the >> migrate_pages >> function also already supports the large folio migration. >> >> So now I did not see any reason to continue restricting NUMA balancing >> for >> large folio. > > I recall John wanted to look into that. CCing him. > > I'll note that the "head page mapcount" heuristic to detect sharers will > now strike on the PTE path and make us believe that a large folios is > exclusive, although it isn't. > > As spelled out in the commit you are referencing: > > commit 6695cf68b15c215d33b8add64c33e01e3cbe236c > Author: Kefeng Wang > Date:   Thu Sep 21 15:44:14 2023 +0800 > >     mm: memory: use a folio in do_numa_page() >     Numa balancing only try to migrate non-compound page in > do_numa_page(), >     use a folio in it to save several compound_head calls, note we use >     folio_estimated_sharers(), it is enough to check the folio sharers > since >     only normal page is handled, if large folio numa balancing is > supported, a >     precise folio sharers check would be used, no functional change > intended. Thanks for pointing out the part I missed. I saw the migrate_pages() syscall is also using folio_estimated_sharers() to check if the folio is shared, and I wonder it will bring about any significant issues? > I'll send WIP patches for one approach that can improve the situation > soonish. Great. Look forward to seeing this:)