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 11161C46CA1 for ; Mon, 18 Sep 2023 07:38:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238569AbjIRHhv (ORCPT ); Mon, 18 Sep 2023 03:37:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56988 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240398AbjIRHhg (ORCPT ); Mon, 18 Sep 2023 03:37:36 -0400 Received: from out30-112.freemail.mail.aliyun.com (out30-112.freemail.mail.aliyun.com [115.124.30.112]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4F6E310F7 for ; Mon, 18 Sep 2023 00:34:26 -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=ay29a033018046059;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=17;SR=0;TI=SMTPD_---0VsIAQZk_1695022459; Received: from 30.97.48.66(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0VsIAQZk_1695022459) by smtp.aliyun-inc.com; Mon, 18 Sep 2023 15:34:21 +0800 Message-ID: <28f76c7c-4b84-5e08-2f27-07592d8078a2@linux.alibaba.com> Date: Mon, 18 Sep 2023 15:34:25 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.15.0 Subject: Re: [RFC PATCH 2/4] mm/compaction: optimize >0 order folio compaction with free page split. To: Zi Yan , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Ryan Roberts , Andrew Morton , "Matthew Wilcox (Oracle)" , David Hildenbrand , "Yin, Fengwei" , Yu Zhao , Vlastimil Babka , Johannes Weiner , Kemeng Shi , Mel Gorman , Rohan Puri , Mcgrof Chamberlain , Adam Manzanares , John Hubbard References: <20230912162815.440749-1-zi.yan@sent.com> <20230912162815.440749-3-zi.yan@sent.com> From: Baolin Wang In-Reply-To: <20230912162815.440749-3-zi.yan@sent.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/13/2023 12:28 AM, Zi Yan wrote: > From: Zi Yan > > During migration in a memory compaction, free pages are placed in an array > of page lists based on their order. But the desired free page order (i.e., > the order of a source page) might not be always present, thus leading to > migration failures. Split a high order free pages when source migration > page has a lower order to increase migration successful rate. > > Note: merging free pages when a migration fails and a lower order free > page is returned via compaction_free() is possible, but there is too much > work. Since the free pages are not buddy pages, it is hard to identify > these free pages using existing PFN-based page merging algorithm. > > Signed-off-by: Zi Yan > --- > mm/compaction.c | 40 +++++++++++++++++++++++++++++++++++++++- > 1 file changed, 39 insertions(+), 1 deletion(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 868e92e55d27..45747ab5f380 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -1801,9 +1801,46 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data) > struct compact_control *cc = (struct compact_control *)data; > struct folio *dst; > int order = folio_order(src); > + bool has_isolated_pages = false; > > +again: > if (!cc->freepages[order].nr_free) { > - isolate_freepages(cc); > + int i; > + > + for (i = order + 1; i <= MAX_ORDER; i++) { > + if (cc->freepages[i].nr_free) { > + struct page *freepage = > + list_first_entry(&cc->freepages[i].pages, > + struct page, lru); > + > + int start_order = i; > + unsigned long size = 1 << start_order; > + > + list_del(&freepage->lru); > + cc->freepages[i].nr_free--; > + > + while (start_order > order) { > + start_order--; > + size >>= 1; > + > + list_add(&freepage[size].lru, > + &cc->freepages[start_order].pages); > + cc->freepages[start_order].nr_free++; > + set_page_private(&freepage[size], start_order); IIUC, these split pages should also call functions to initialize? e.g. prep_compound_page()? > + } > + post_alloc_hook(freepage, order, __GFP_MOVABLE); > + if (order) > + prep_compound_page(freepage, order); > + dst = page_folio(freepage); > + goto done; > + } > + } > + if (!has_isolated_pages) { > + isolate_freepages(cc); > + has_isolated_pages = true; > + goto again; > + } > + > if (!cc->freepages[order].nr_free) > return NULL; > } > @@ -1814,6 +1851,7 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data) > post_alloc_hook(&dst->page, order, __GFP_MOVABLE); > if (order) > prep_compound_page(&dst->page, order); > +done: > cc->nr_freepages -= 1 << order; > return dst; > }