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=-14.1 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED, 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 9AD2DC433DF for ; Tue, 18 Aug 2020 06:51:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7B1C120639 for ; Tue, 18 Aug 2020 06:51:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726648AbgHRGve (ORCPT ); Tue, 18 Aug 2020 02:51:34 -0400 Received: from out30-130.freemail.mail.aliyun.com ([115.124.30.130]:59555 "EHLO out30-130.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726228AbgHRGvb (ORCPT ); Tue, 18 Aug 2020 02:51:31 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R651e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01f04427;MF=alex.shi@linux.alibaba.com;NM=1;PH=DS;RN=19;SR=0;TI=SMTPD_---0U67H.h6_1597733485; Received: from IT-FVFX43SYHV2H.local(mailfrom:alex.shi@linux.alibaba.com fp:SMTPD_---0U67H.h6_1597733485) by smtp.aliyun-inc.com(127.0.0.1); Tue, 18 Aug 2020 14:51:26 +0800 Subject: Re: [RFC PATCH 2/3] mm: Drop use of test_and_set_skip in favor of just setting skip To: Alexander Duyck Cc: yang.shi@linux.alibaba.com, lkp@intel.com, rong.a.chen@intel.com, khlebnikov@yandex-team.ru, kirill@shutemov.name, hughd@google.com, linux-kernel@vger.kernel.org, daniel.m.jordan@oracle.com, linux-mm@kvack.org, shakeelb@google.com, willy@infradead.org, hannes@cmpxchg.org, tj@kernel.org, cgroups@vger.kernel.org, akpm@linux-foundation.org, richard.weiyang@gmail.com, mgorman@techsingularity.net, iamjoonsoo.kim@lge.com References: <20200813035100.13054.25671.stgit@localhost.localdomain> <20200813040232.13054.82417.stgit@localhost.localdomain> From: Alex Shi Message-ID: <176fae1b-b95b-51c3-d8cc-4380f0972666@linux.alibaba.com> Date: Tue, 18 Aug 2020 14:50:25 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200813040232.13054.82417.stgit@localhost.localdomain> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2020/8/13 下午12:02, Alexander Duyck 写道: > From: Alexander Duyck > > The only user of test_and_set_skip was isolate_migratepages_block and it > was using it after a call that was testing and clearing the LRU flag. As > such it really didn't need to be behind the LRU lock anymore as it wasn't > really fulfilling its purpose. > > With that being the case we can simply drop the bit and instead directly > just call the set_pageblock_skip function if the page we are working on is > the valid_page at the start of the pageblock. It shouldn't be possible for > us to encounter the bit being set since we obtained the LRU flag for the > first page in the pageblock which means we would have exclusive access to > setting the skip bit. As such we don't need to worry about the abort case > since no other thread will be able to call what used to be > test_and_set_skip. > > Since we have dropped the late abort case we can drop the code that was > clearing the LRU flag and calling page_put since the abort case will now > not be holding a reference to a page. > > Signed-off-by: Alexander Duyck After my false sharing remove on pageblock_flags, this patch looks fine with a minor change > --- > mm/compaction.c | 50 +++++++------------------------------------------- > 1 file changed, 7 insertions(+), 43 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 5021a18ef722..c1e9918f9dd4 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -399,29 +399,6 @@ void reset_isolation_suitable(pg_data_t *pgdat) > } > } > > -/* > - * Sets the pageblock skip bit if it was clear. Note that this is a hint as > - * locks are not required for read/writers. Returns true if it was already set. > - */ > -static bool test_and_set_skip(struct compact_control *cc, struct page *page, > - unsigned long pfn) > -{ > - bool skip; > - > - /* Do no update if skip hint is being ignored */ > - if (cc->ignore_skip_hint) > - return false; > - > - if (!IS_ALIGNED(pfn, pageblock_nr_pages)) > - return false; > - > - skip = get_pageblock_skip(page); > - if (!skip && !cc->no_set_skip_hint) > - skip = !set_pageblock_skip(page); > - > - return skip; > -} > - > static void update_cached_migrate(struct compact_control *cc, unsigned long pfn) > { > struct zone *zone = cc->zone; > @@ -480,12 +457,6 @@ static inline void update_pageblock_skip(struct compact_control *cc, > static void update_cached_migrate(struct compact_control *cc, unsigned long pfn) > { > } > - > -static bool test_and_set_skip(struct compact_control *cc, struct page *page, > - unsigned long pfn) > -{ > - return false; > -} > #endif /* CONFIG_COMPACTION */ > > /* > @@ -895,7 +866,6 @@ static bool too_many_isolated(pg_data_t *pgdat) > if (!valid_page && IS_ALIGNED(low_pfn, pageblock_nr_pages)) { > if (!cc->ignore_skip_hint && get_pageblock_skip(page)) { > low_pfn = end_pfn; > - page = NULL; > goto isolate_abort; > } > valid_page = page; > @@ -991,6 +961,13 @@ static bool too_many_isolated(pg_data_t *pgdat) > if (!TestClearPageLRU(page)) > goto isolate_fail_put; > > + /* Indicate that we want exclusive access to this pageblock */ > + if (page == valid_page) { > + skip_updated = true; > + if (!cc->ignore_skip_hint) if (!cc->ignore_skip_hint && !cc->no_set_skip_hint) no_set_skip_hint needs to add here. Thanks Alex > + set_pageblock_skip(page); > + } > + > /* If we already hold the lock, we can skip some rechecking */ > if (!lruvec || !lruvec_holds_page_lru_lock(page, lruvec)) { > if (lruvec) > @@ -1002,13 +979,6 @@ static bool too_many_isolated(pg_data_t *pgdat) > > lruvec_memcg_debug(lruvec, page); > > - /* Try get exclusive access under lock */ > - if (!skip_updated) { > - skip_updated = true; > - if (test_and_set_skip(cc, page, low_pfn)) > - goto isolate_abort; > - } > - > /* > * Page become compound since the non-locked check, > * and it's on LRU. It can only be a THP so the order > @@ -1094,15 +1064,9 @@ static bool too_many_isolated(pg_data_t *pgdat) > if (unlikely(low_pfn > end_pfn)) > low_pfn = end_pfn; > > - page = NULL; > - > isolate_abort: > if (lruvec) > unlock_page_lruvec_irqrestore(lruvec, flags); > - if (page) { > - SetPageLRU(page); > - put_page(page); > - } > > /* > * Updated the cached scanner pfn once the pageblock has been scanned > From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Shi Subject: Re: [RFC PATCH 2/3] mm: Drop use of test_and_set_skip in favor of just setting skip Date: Tue, 18 Aug 2020 14:50:25 +0800 Message-ID: <176fae1b-b95b-51c3-d8cc-4380f0972666@linux.alibaba.com> References: <20200813035100.13054.25671.stgit@localhost.localdomain> <20200813040232.13054.82417.stgit@localhost.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20200813040232.13054.82417.stgit-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="utf-8" To: Alexander Duyck Cc: yang.shi-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org, lkp-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, rong.a.chen-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, khlebnikov-XoJtRXgx1JseBXzfvpsJ4g@public.gmane.org, kirill-oKw7cIdHH8eLwutG50LtGA@public.gmane.org, hughd-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, daniel.m.jordan-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, willy-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, mgorman-3eNAlZScCAx27rWaFMvyedHuzzzSOjJt@public.gmane.org, iamjoonsoo.kim-Hm3cg6mZ9cc@public.gmane.org 在 2020/8/13 下午12:02, Alexander Duyck 写道: > From: Alexander Duyck > > The only user of test_and_set_skip was isolate_migratepages_block and it > was using it after a call that was testing and clearing the LRU flag. As > such it really didn't need to be behind the LRU lock anymore as it wasn't > really fulfilling its purpose. > > With that being the case we can simply drop the bit and instead directly > just call the set_pageblock_skip function if the page we are working on is > the valid_page at the start of the pageblock. It shouldn't be possible for > us to encounter the bit being set since we obtained the LRU flag for the > first page in the pageblock which means we would have exclusive access to > setting the skip bit. As such we don't need to worry about the abort case > since no other thread will be able to call what used to be > test_and_set_skip. > > Since we have dropped the late abort case we can drop the code that was > clearing the LRU flag and calling page_put since the abort case will now > not be holding a reference to a page. > > Signed-off-by: Alexander Duyck After my false sharing remove on pageblock_flags, this patch looks fine with a minor change > --- > mm/compaction.c | 50 +++++++------------------------------------------- > 1 file changed, 7 insertions(+), 43 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 5021a18ef722..c1e9918f9dd4 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -399,29 +399,6 @@ void reset_isolation_suitable(pg_data_t *pgdat) > } > } > > -/* > - * Sets the pageblock skip bit if it was clear. Note that this is a hint as > - * locks are not required for read/writers. Returns true if it was already set. > - */ > -static bool test_and_set_skip(struct compact_control *cc, struct page *page, > - unsigned long pfn) > -{ > - bool skip; > - > - /* Do no update if skip hint is being ignored */ > - if (cc->ignore_skip_hint) > - return false; > - > - if (!IS_ALIGNED(pfn, pageblock_nr_pages)) > - return false; > - > - skip = get_pageblock_skip(page); > - if (!skip && !cc->no_set_skip_hint) > - skip = !set_pageblock_skip(page); > - > - return skip; > -} > - > static void update_cached_migrate(struct compact_control *cc, unsigned long pfn) > { > struct zone *zone = cc->zone; > @@ -480,12 +457,6 @@ static inline void update_pageblock_skip(struct compact_control *cc, > static void update_cached_migrate(struct compact_control *cc, unsigned long pfn) > { > } > - > -static bool test_and_set_skip(struct compact_control *cc, struct page *page, > - unsigned long pfn) > -{ > - return false; > -} > #endif /* CONFIG_COMPACTION */ > > /* > @@ -895,7 +866,6 @@ static bool too_many_isolated(pg_data_t *pgdat) > if (!valid_page && IS_ALIGNED(low_pfn, pageblock_nr_pages)) { > if (!cc->ignore_skip_hint && get_pageblock_skip(page)) { > low_pfn = end_pfn; > - page = NULL; > goto isolate_abort; > } > valid_page = page; > @@ -991,6 +961,13 @@ static bool too_many_isolated(pg_data_t *pgdat) > if (!TestClearPageLRU(page)) > goto isolate_fail_put; > > + /* Indicate that we want exclusive access to this pageblock */ > + if (page == valid_page) { > + skip_updated = true; > + if (!cc->ignore_skip_hint) if (!cc->ignore_skip_hint && !cc->no_set_skip_hint) no_set_skip_hint needs to add here. Thanks Alex > + set_pageblock_skip(page); > + } > + > /* If we already hold the lock, we can skip some rechecking */ > if (!lruvec || !lruvec_holds_page_lru_lock(page, lruvec)) { > if (lruvec) > @@ -1002,13 +979,6 @@ static bool too_many_isolated(pg_data_t *pgdat) > > lruvec_memcg_debug(lruvec, page); > > - /* Try get exclusive access under lock */ > - if (!skip_updated) { > - skip_updated = true; > - if (test_and_set_skip(cc, page, low_pfn)) > - goto isolate_abort; > - } > - > /* > * Page become compound since the non-locked check, > * and it's on LRU. It can only be a THP so the order > @@ -1094,15 +1064,9 @@ static bool too_many_isolated(pg_data_t *pgdat) > if (unlikely(low_pfn > end_pfn)) > low_pfn = end_pfn; > > - page = NULL; > - > isolate_abort: > if (lruvec) > unlock_page_lruvec_irqrestore(lruvec, flags); > - if (page) { > - SetPageLRU(page); > - put_page(page); > - } > > /* > * Updated the cached scanner pfn once the pageblock has been scanned >