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 85171C61D9B for ; Wed, 22 Nov 2023 10:26:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235198AbjKVK1A (ORCPT ); Wed, 22 Nov 2023 05:27:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43882 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234934AbjKVK0q (ORCPT ); Wed, 22 Nov 2023 05:26:46 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 124E71AA for ; Wed, 22 Nov 2023 02:26:34 -0800 (PST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 891551595; Wed, 22 Nov 2023 02:27:20 -0800 (PST) Received: from [10.57.71.201] (unknown [10.57.71.201]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4340D3F6C4; Wed, 22 Nov 2023 02:26:31 -0800 (PST) Message-ID: Date: Wed, 22 Nov 2023 10:26:29 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 3/4] mm/compaction: optimize >0 order folio compaction with free page split. Content-Language: en-GB To: Zi Yan , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: "Huang, Ying" , Andrew Morton , "Matthew Wilcox (Oracle)" , David Hildenbrand , "Yin, Fengwei" , Yu Zhao , Vlastimil Babka , "Kirill A . Shutemov" , Johannes Weiner , Baolin Wang , Kemeng Shi , Mel Gorman , Rohan Puri , Mcgrof Chamberlain , Adam Manzanares , "Vishal Moola (Oracle)" References: <20231113170157.280181-1-zi.yan@sent.com> <20231113170157.280181-4-zi.yan@sent.com> From: Ryan Roberts In-Reply-To: <20231113170157.280181-4-zi.yan@sent.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 13/11/2023 17:01, 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 ec6b5cc7e907..9c083e6b399a 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -1806,9 +1806,46 @@ 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_pages) { > - isolate_freepages(cc); > + int i; > + > + for (i = order + 1; i <= MAX_ORDER; i++) { > + if (cc->freepages[i].nr_pages) { > + 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_pages--; > + > + while (start_order > order) { > + start_order--; > + size >>= 1; > + > + list_add(&freepage[size].lru, > + &cc->freepages[start_order].pages); > + cc->freepages[start_order].nr_pages++; > + set_page_private(&freepage[size], start_order); > + } > + post_alloc_hook(freepage, order, __GFP_MOVABLE); > + if (order) > + prep_compound_page(freepage, order); > + dst = page_folio(freepage); > + goto done; Perhaps just do: dst = (struct folio *)freepage; goto done; then move done: up a couple of statements below, so that post_alloc_hook() and prep_compound_page() are always done below in common path? Although perhaps the cast is frowned upon, you're already making the assumption that page and folio are interchangable the way you call list_first_entry(). > + } > + } > + if (!has_isolated_pages) { > + isolate_freepages(cc); > + has_isolated_pages = true; > + goto again; > + } > + > if (!cc->freepages[order].nr_pages) > return NULL; > } > @@ -1819,6 +1856,7 @@ 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 page_rmappable_folio(&dst->page); > }