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 X-Spam-Level: X-Spam-Status: No, score=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7607CC5519F for ; Sun, 22 Nov 2020 14:02:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4260620782 for ; Sun, 22 Nov 2020 14:02:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727850AbgKVOCO (ORCPT ); Sun, 22 Nov 2020 09:02:14 -0500 Received: from out30-45.freemail.mail.aliyun.com ([115.124.30.45]:37981 "EHLO out30-45.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727567AbgKVOCO (ORCPT ); Sun, 22 Nov 2020 09:02:14 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R421e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04407;MF=alex.shi@linux.alibaba.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---0UG8gdoX_1606053728; Received: from IT-FVFX43SYHV2H.lan(mailfrom:alex.shi@linux.alibaba.com fp:SMTPD_---0UG8gdoX_1606053728) by smtp.aliyun-inc.com(127.0.0.1); Sun, 22 Nov 2020 22:02:09 +0800 Subject: Re: [PATCH next] mm/vmscan: __isolate_lru_page_prepare clean up To: Matthew Wilcox Cc: Andrew Morton , Hugh Dickins , Yu Zhao , Vlastimil Babka , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <1605859413-53864-1-git-send-email-alex.shi@linux.alibaba.com> <20201120151307.4d9e3ef092ba01a325db7ce2@linux-foundation.org> <20201122123552.GF4327@casper.infradead.org> From: Alex Shi Message-ID: <728874d7-2d93-4049-68c1-dcc3b2d52ccd@linux.alibaba.com> Date: Sun, 22 Nov 2020 22:00:24 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20201122123552.GF4327@casper.infradead.org> Content-Type: text/plain; charset=gbk Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ÔÚ 2020/11/22 ÏÂÎç8:35, Matthew Wilcox дµÀ: > On Sun, Nov 22, 2020 at 08:00:19PM +0800, Alex Shi wrote: >> mm/compaction.c | 2 +- >> mm/vmscan.c | 69 +++++++++++++++++++++++-------------------------- >> 2 files changed, 34 insertions(+), 37 deletions(-) > > How is it possible you're changing the signature of a function without > touching a header file? Surely __isolate_lru_page_prepare() must be declared > in mm/internal.h ? > >> +++ b/mm/vmscan.c >> @@ -1536,19 +1536,17 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone, >> * page: page to consider >> * mode: one of the LRU isolation modes defined above >> * >> - * returns 0 on success, -ve errno on failure. >> + * returns ture on success, false on failure. > > "true". > >> @@ -1674,35 +1672,34 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, >> * only when the page is being freed somewhere else. >> */ >> scan += nr_pages; >> - switch (__isolate_lru_page_prepare(page, mode)) { >> - case 0: >> + if (!__isolate_lru_page_prepare(page, mode)) { >> + /* else it is being freed elsewhere */ > > I don't think the word "else" helps here. Just > /* It is being freed elsewhere */ > >> + if (!TestClearPageLRU(page)) { >> /* >> + * This page may in other isolation path, >> + * but we still hold lru_lock. >> */ > > I don't think this comment helps me understand what's going on here. > Maybe: > > /* Another thread is already isolating this page */ > >> + put_page(page); >> list_move(&page->lru, src); >> + continue; >> } Hi Matthew, Thanks a lot for all comments, I picked all up and here is the v3: >From 167131dd106a96fd08af725df850e0da6ec899af Mon Sep 17 00:00:00 2001 From: Alex Shi Date: Fri, 20 Nov 2020 14:49:16 +0800 Subject: [PATCH v3 next] mm/vmscan: __isolate_lru_page_prepare clean up The function just return 2 results, so use a 'switch' to deal with its result is unnecessary, and simplify it to a bool func as Vlastimil suggested. Also remove 'goto' by reusing list_move(), and take Matthew Wilcox's suggestion to update comments in function. Signed-off-by: Alex Shi Cc: Andrew Morton Cc: Matthew Wilcox Cc: Hugh Dickins Cc: Yu Zhao Cc: Vlastimil Babka Cc: Michal Hocko Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org --- include/linux/swap.h | 2 +- mm/compaction.c | 2 +- mm/vmscan.c | 68 ++++++++++++++++++++------------------------ 3 files changed, 33 insertions(+), 39 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index 596bc2f4d9b0..5bba15ac5a2e 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -356,7 +356,7 @@ extern void lru_cache_add_inactive_or_unevictable(struct page *page, extern unsigned long zone_reclaimable_pages(struct zone *zone); extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order, gfp_t gfp_mask, nodemask_t *mask); -extern int __isolate_lru_page_prepare(struct page *page, isolate_mode_t mode); +extern bool __isolate_lru_page_prepare(struct page *page, isolate_mode_t mode); extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg, unsigned long nr_pages, gfp_t gfp_mask, diff --git a/mm/compaction.c b/mm/compaction.c index b68931854253..8d71ffebe6cb 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -988,7 +988,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, if (unlikely(!get_page_unless_zero(page))) goto isolate_fail; - if (__isolate_lru_page_prepare(page, isolate_mode) != 0) + if (!__isolate_lru_page_prepare(page, isolate_mode)) goto isolate_fail_put; /* Try isolate the page */ diff --git a/mm/vmscan.c b/mm/vmscan.c index c6f94e55c3fe..4d2703c43310 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1536,19 +1536,17 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone, * page: page to consider * mode: one of the LRU isolation modes defined above * - * returns 0 on success, -ve errno on failure. + * returns true on success, false on failure. */ -int __isolate_lru_page_prepare(struct page *page, isolate_mode_t mode) +bool __isolate_lru_page_prepare(struct page *page, isolate_mode_t mode) { - int ret = -EBUSY; - /* Only take pages on the LRU. */ if (!PageLRU(page)) - return ret; + return false; /* Compaction should not handle unevictable pages but CMA can do so */ if (PageUnevictable(page) && !(mode & ISOLATE_UNEVICTABLE)) - return ret; + return false; /* * To minimise LRU disruption, the caller can indicate that it only @@ -1561,7 +1559,7 @@ int __isolate_lru_page_prepare(struct page *page, isolate_mode_t mode) if (mode & ISOLATE_ASYNC_MIGRATE) { /* All the caller can do on PageWriteback is block */ if (PageWriteback(page)) - return ret; + return false; if (PageDirty(page)) { struct address_space *mapping; @@ -1577,20 +1575,20 @@ int __isolate_lru_page_prepare(struct page *page, isolate_mode_t mode) * from the page cache. */ if (!trylock_page(page)) - return ret; + return false; mapping = page_mapping(page); migrate_dirty = !mapping || mapping->a_ops->migratepage; unlock_page(page); if (!migrate_dirty) - return ret; + return false; } } if ((mode & ISOLATE_UNMAPPED) && page_mapped(page)) - return ret; + return false; - return 0; + return true; } /* @@ -1674,35 +1672,31 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, * only when the page is being freed somewhere else. */ scan += nr_pages; - switch (__isolate_lru_page_prepare(page, mode)) { - case 0: - /* - * Be careful not to clear PageLRU until after we're - * sure the page is not being freed elsewhere -- the - * page release code relies on it. - */ - if (unlikely(!get_page_unless_zero(page))) - goto busy; - - if (!TestClearPageLRU(page)) { - /* - * This page may in other isolation path, - * but we still hold lru_lock. - */ - put_page(page); - goto busy; - } - - nr_taken += nr_pages; - nr_zone_taken[page_zonenum(page)] += nr_pages; - list_move(&page->lru, dst); - break; + if (!__isolate_lru_page_prepare(page, mode)) { + /* It is being freed elsewhere */ + list_move(&page->lru, src); + continue; + } + /* + * Be careful not to clear PageLRU until after we're + * sure the page is not being freed elsewhere -- the + * page release code relies on it. + */ + if (unlikely(!get_page_unless_zero(page))) { + list_move(&page->lru, src); + continue; + } - default: -busy: - /* else it is being freed elsewhere */ + if (!TestClearPageLRU(page)) { + /* Another thread is already isolating this page */ + put_page(page); list_move(&page->lru, src); + continue; } + + nr_taken += nr_pages; + nr_zone_taken[page_zonenum(page)] += nr_pages; + list_move(&page->lru, dst); } /* -- 2.29.GIT