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 D3ADAEE6447 for ; Fri, 15 Sep 2023 09:33:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233656AbjIOJde (ORCPT ); Fri, 15 Sep 2023 05:33:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40570 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233351AbjIOJdc (ORCPT ); Fri, 15 Sep 2023 05:33:32 -0400 Received: from out30-100.freemail.mail.aliyun.com (out30-100.freemail.mail.aliyun.com [115.124.30.100]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E6C61CED for ; Fri, 15 Sep 2023 02:33:26 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R571e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046049;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=17;SR=0;TI=SMTPD_---0Vs6ltje_1694770402; Received: from 30.97.48.69(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0Vs6ltje_1694770402) by smtp.aliyun-inc.com; Fri, 15 Sep 2023 17:33:23 +0800 Message-ID: <1d2e6eff-027b-bf27-924d-c232667d0845@linux.alibaba.com> Date: Fri, 15 Sep 2023 17:33:28 +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 1/4] mm/compaction: add support for >0 order folio memory compaction. 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> <20230912162815.440749-2-zi.yan@sent.com> From: Baolin Wang In-Reply-To: <20230912162815.440749-2-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 > > Before, memory compaction only migrates order-0 folios and skips >0 order > folios. This commit adds support for >0 order folio compaction by keeping > isolated free pages at their original size without splitting them into > order-0 pages and using them directly during migration process. > > What is different from the prior implementation: > 1. All isolated free pages are kept in a MAX_ORDER+1 array of page lists, > where each page list stores free pages in the same order. > 2. All free pages are not post_alloc_hook() processed nor buddy pages, > although their orders are stored in first page's private like buddy > pages. > 3. During migration, in new page allocation time (i.e., in > compaction_alloc()), free pages are then processed by post_alloc_hook(). > When migration fails and a new page is returned (i.e., in > compaction_free()), free pages are restored by reversing the > post_alloc_hook() operations. > > Step 3 is done for a latter optimization that splitting and/or merging free > pages during compaction becomes easier. > > Signed-off-by: Zi Yan > --- > mm/compaction.c | 108 +++++++++++++++++++++++++++++++++++++++--------- > mm/internal.h | 7 +++- > 2 files changed, 94 insertions(+), 21 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 01ba298739dd..868e92e55d27 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -107,6 +107,44 @@ static void split_map_pages(struct list_head *list) > list_splice(&tmp_list, list); > } > > +static unsigned long release_free_list(struct free_list *freepages) > +{ > + int order; > + unsigned long high_pfn = 0; > + > + for (order = 0; order <= MAX_ORDER; order++) { > + struct page *page, *next; > + > + list_for_each_entry_safe(page, next, &freepages[order].pages, lru) { > + unsigned long pfn = page_to_pfn(page); > + > + list_del(&page->lru); > + /* > + * Convert free pages into post allocation pages, so > + * that we can free them via __free_page. > + */ > + post_alloc_hook(page, order, __GFP_MOVABLE); > + __free_pages(page, order); > + if (pfn > high_pfn) > + high_pfn = pfn; > + } > + } > + return high_pfn; > +} > + > +static void sort_free_pages(struct list_head *src, struct free_list *dst) > +{ > + unsigned int order; > + struct page *page, *next; > + > + list_for_each_entry_safe(page, next, src, lru) { > + order = buddy_order(page); These pages are already isolated from the buddy system, but continue to use buddy_order() to get the page order, which can be confused. Moreover, the buddy_order() should be under the zone lock protection. IMO, just use 'page_private()' to get the page order like split_map_pages() already did, that seems more readable. > + > + list_move(&page->lru, &dst[order].pages); > + dst[order].nr_free++; > + } > +} > + > #ifdef CONFIG_COMPACTION > bool PageMovable(struct page *page) > { > @@ -1422,6 +1460,7 @@ fast_isolate_around(struct compact_control *cc, unsigned long pfn) > { > unsigned long start_pfn, end_pfn; > struct page *page; > + LIST_HEAD(freelist); > > /* Do not search around if there are enough pages already */ > if (cc->nr_freepages >= cc->nr_migratepages) > @@ -1439,7 +1478,8 @@ fast_isolate_around(struct compact_control *cc, unsigned long pfn) > if (!page) > return; > > - isolate_freepages_block(cc, &start_pfn, end_pfn, &cc->freepages, 1, false); > + isolate_freepages_block(cc, &start_pfn, end_pfn, &freelist, 1, false); > + sort_free_pages(&freelist, cc->freepages); > > /* Skip this pageblock in the future as it's full or nearly full */ > if (start_pfn == end_pfn && !cc->no_set_skip_hint) > @@ -1568,7 +1608,7 @@ static void fast_isolate_freepages(struct compact_control *cc) > nr_scanned += nr_isolated - 1; > total_isolated += nr_isolated; > cc->nr_freepages += nr_isolated; > - list_add_tail(&page->lru, &cc->freepages); > + list_add_tail(&page->lru, &cc->freepages[order].pages); Missed to update cc->freepages[order].nr_free? > count_compact_events(COMPACTISOLATED, nr_isolated); > } else { > /* If isolation fails, abort the search */ > @@ -1642,13 +1682,13 @@ static void isolate_freepages(struct compact_control *cc) > unsigned long isolate_start_pfn; /* exact pfn we start at */ > unsigned long block_end_pfn; /* end of current pageblock */ > unsigned long low_pfn; /* lowest pfn scanner is able to scan */ > - struct list_head *freelist = &cc->freepages; > unsigned int stride; > + LIST_HEAD(freelist); > > /* Try a small search of the free lists for a candidate */ > fast_isolate_freepages(cc); > if (cc->nr_freepages) > - goto splitmap; > + return; > > /* > * Initialise the free scanner. The starting point is where we last > @@ -1708,7 +1748,8 @@ static void isolate_freepages(struct compact_control *cc) > > /* Found a block suitable for isolating free pages from. */ > nr_isolated = isolate_freepages_block(cc, &isolate_start_pfn, > - block_end_pfn, freelist, stride, false); > + block_end_pfn, &freelist, stride, false); > + sort_free_pages(&freelist, cc->freepages); > > /* Update the skip hint if the full pageblock was scanned */ > if (isolate_start_pfn == block_end_pfn) > @@ -1749,10 +1790,6 @@ static void isolate_freepages(struct compact_control *cc) > * and the loop terminated due to isolate_start_pfn < low_pfn > */ > cc->free_pfn = isolate_start_pfn; > - > -splitmap: > - /* __isolate_free_page() does not map the pages */ > - split_map_pages(freelist); > } > > /* > @@ -1763,18 +1800,21 @@ 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); > > - if (list_empty(&cc->freepages)) { > + if (!cc->freepages[order].nr_free) { > isolate_freepages(cc); > - > - if (list_empty(&cc->freepages)) > + if (!cc->freepages[order].nr_free) > return NULL; > } > > - dst = list_entry(cc->freepages.next, struct folio, lru); > + dst = list_first_entry(&cc->freepages[order].pages, struct folio, lru); > + cc->freepages[order].nr_free--; > list_del(&dst->lru); > - cc->nr_freepages--; > - > + post_alloc_hook(&dst->page, order, __GFP_MOVABLE); > + if (order) > + prep_compound_page(&dst->page, order); > + cc->nr_freepages -= 1 << order; > return dst; > } > > @@ -1786,9 +1826,34 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data) > static void compaction_free(struct folio *dst, unsigned long data) > { > struct compact_control *cc = (struct compact_control *)data; > + int order = folio_order(dst); > + struct page *page = &dst->page; > > - list_add(&dst->lru, &cc->freepages); > - cc->nr_freepages++; > + if (order) { > + int i; > + > + page[1].flags &= ~PAGE_FLAGS_SECOND; > + for (i = 1; i < (1 << order); i++) { > + page[i].mapping = NULL; > + clear_compound_head(&page[i]); > + page[i].flags &= ~PAGE_FLAGS_CHECK_AT_PREP; > + } > + > + } > + /* revert post_alloc_hook() operations */ > + page->mapping = NULL; > + page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; > + set_page_count(page, 0); > + page_mapcount_reset(page); > + reset_page_owner(page, order); > + page_table_check_free(page, order); > + arch_free_page(page, order); > + set_page_private(page, order); > + INIT_LIST_HEAD(&dst->lru); > + > + list_add(&dst->lru, &cc->freepages[order].pages); > + cc->freepages[order].nr_free++; > + cc->nr_freepages += 1 << order; > } > > /* possible outcome of isolate_migratepages */ > @@ -2412,6 +2477,7 @@ compact_zone(struct compact_control *cc, struct capture_control *capc) > const bool sync = cc->mode != MIGRATE_ASYNC; > bool update_cached; > unsigned int nr_succeeded = 0; > + int order; > > /* > * These counters track activities during zone compaction. Initialize > @@ -2421,7 +2487,10 @@ compact_zone(struct compact_control *cc, struct capture_control *capc) > cc->total_free_scanned = 0; > cc->nr_migratepages = 0; > cc->nr_freepages = 0; > - INIT_LIST_HEAD(&cc->freepages); > + for (order = 0; order <= MAX_ORDER; order++) { > + INIT_LIST_HEAD(&cc->freepages[order].pages); > + cc->freepages[order].nr_free = 0; > + } > INIT_LIST_HEAD(&cc->migratepages); > > cc->migratetype = gfp_migratetype(cc->gfp_mask); > @@ -2607,7 +2676,7 @@ compact_zone(struct compact_control *cc, struct capture_control *capc) > * so we don't leave any returned pages behind in the next attempt. > */ > if (cc->nr_freepages > 0) { > - unsigned long free_pfn = release_freepages(&cc->freepages); > + unsigned long free_pfn = release_free_list(cc->freepages); > > cc->nr_freepages = 0; > VM_BUG_ON(free_pfn == 0); > @@ -2626,7 +2695,6 @@ compact_zone(struct compact_control *cc, struct capture_control *capc) > > trace_mm_compaction_end(cc, start_pfn, end_pfn, sync, ret); > > - VM_BUG_ON(!list_empty(&cc->freepages)); > VM_BUG_ON(!list_empty(&cc->migratepages)); > > return ret; > diff --git a/mm/internal.h b/mm/internal.h > index 8c90e966e9f8..f5c691bb5c1c 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -465,6 +465,11 @@ int split_free_page(struct page *free_page, > /* > * in mm/compaction.c > */ > + > +struct free_list { > + struct list_head pages; > + unsigned long nr_free; > +}; > /* > * compact_control is used to track pages being migrated and the free pages > * they are being migrated to during memory compaction. The free_pfn starts > @@ -473,7 +478,7 @@ int split_free_page(struct page *free_page, > * completes when free_pfn <= migrate_pfn > */ > struct compact_control { > - struct list_head freepages; /* List of free pages to migrate to */ > + struct free_list freepages[MAX_ORDER + 1]; /* List of free pages to migrate to */ > struct list_head migratepages; /* List of pages being migrated */ > unsigned int nr_freepages; /* Number of isolated free pages */ > unsigned int nr_migratepages; /* Number of pages to migrate */