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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 38082C2BB48 for ; Tue, 15 Dec 2020 22:20:29 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C2A9522D06 for ; Tue, 15 Dec 2020 22:20:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C2A9522D06 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 5B31F6B0071; Tue, 15 Dec 2020 17:20:28 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 562F16B0072; Tue, 15 Dec 2020 17:20:28 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 402F56B0073; Tue, 15 Dec 2020 17:20:28 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0213.hostedemail.com [216.40.44.213]) by kanga.kvack.org (Postfix) with ESMTP id 24F6E6B0071 for ; Tue, 15 Dec 2020 17:20:28 -0500 (EST) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id E509D180AD81A for ; Tue, 15 Dec 2020 22:20:27 +0000 (UTC) X-FDA: 77596936494.08.lock70_2a0fa6127427 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin08.hostedemail.com (Postfix) with ESMTP id C5B6C1819E76B for ; Tue, 15 Dec 2020 22:20:27 +0000 (UTC) X-HE-Tag: lock70_2a0fa6127427 X-Filterd-Recvd-Size: 7731 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf08.hostedemail.com (Postfix) with ESMTP for ; Tue, 15 Dec 2020 22:20:27 +0000 (UTC) Date: Tue, 15 Dec 2020 14:20:24 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1608070826; bh=igu9+jhjsJ6nopit9khbzJNO1kBtIiPPb8A34akUTv4=; h=From:To:Subject:In-Reply-To:From; b=fYK7897ikit7YrunpoGNWcfXNNTBl2EAPV0O+DIXhW/ozFeaTxCjg4McFpY52kXGQ rO/AS5DpUlqu45Kzpaj0aXAseY+7YGDFKjummPTIfLYyAsf6VtVIohH+65Fwob6Dcn rM6gn8YoOzEr2P6dqT3pIO2hipr6Pf4hiqyGO4c8= From: Andrew Morton To: aarcange@redhat.com, akpm@linux-foundation.org, alex.shi@linux.alibaba.com, alexander.duyck@gmail.com, aryabinin@virtuozzo.com, daniel.m.jordan@oracle.com, hannes@cmpxchg.org, hughd@google.com, iamjoonsoo.kim@lge.com, jannh@google.com, khlebnikov@yandex-team.ru, kirill.shutemov@linux.intel.com, kirill@shutemov.name, linux-mm@kvack.org, mgorman@techsingularity.net, mhocko@kernel.org, mhocko@suse.com, mika.penttila@nextfour.com, minchan@kernel.org, mm-commits@vger.kernel.org, richard.weiyang@gmail.com, rong.a.chen@intel.com, shakeelb@google.com, tglx@linutronix.de, tj@kernel.org, torvalds@linux-foundation.org, vbabka@suse.cz, vdavydov.dev@gmail.com, willy@infradead.org, yang.shi@linux.alibaba.com, ying.huang@intel.com Subject: [patch 04/19] mm/thp: narrow lru locking Message-ID: <20201215222024.XDeNGvndP%akpm@linux-foundation.org> In-Reply-To: <20201215123253.954eca9a5ef4c0d52fd381fa@linux-foundation.org> User-Agent: s-nail v14.8.16 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: =46rom: Alex Shi Subject: mm/thp: narrow lru locking lru_lock and page cache xa_lock have no obvious reason to be taken one way round or the other: until now, lru_lock has been taken before page cache xa_lock, when splitting a THP; but nothing else takes them together.=20 Reverse that ordering: let's narrow the lru locking - but leave local_irq_disable to block interrupts throughout, like before. Hugh Dickins point: split_huge_page_to_list() was already silly, to be using the _irqsave variant: it's just been taking sleeping locks, so would already be broken if entered with interrupts enabled. So we can save passing flags argument down to __split_huge_page(). Why change the lock ordering here? That was hard to decide. One reason: when this series reaches per-memcg lru locking, it relies on the THP's memcg to be stable when taking the lru_lock: that is now done after the THP's refcount has been frozen, which ensures page memcg cannot change. Another reason: previously, lock_page_memcg()'s move_lock was presumed to nest inside lru_lock; but now lru_lock must nest inside (page cache lock inside) move_lock, so it becomes possible to use lock_page_memcg() to stabilize page memcg before taking its lru_lock. That is not the mechanism used in this series, but it is an option we want to keep open. [hughd@google.com: rewrite commit log] Link: https://lkml.kernel.org/r/1604566549-62481-5-git-send-email-alex.shi@= linux.alibaba.com Signed-off-by: Alex Shi Reviewed-by: Kirill A. Shutemov Acked-by: Hugh Dickins Cc: Kirill A. Shutemov Cc: Andrea Arcangeli Cc: Johannes Weiner Cc: Matthew Wilcox Cc: Alexander Duyck Cc: Andrey Ryabinin Cc: "Chen, Rong A" Cc: Daniel Jordan Cc: "Huang, Ying" Cc: Jann Horn Cc: Joonsoo Kim Cc: Konstantin Khlebnikov Cc: Mel Gorman Cc: Michal Hocko Cc: Michal Hocko Cc: Mika Penttil=C3=A4 Cc: Minchan Kim Cc: Shakeel Butt Cc: Tejun Heo Cc: Thomas Gleixner Cc: Vladimir Davydov Cc: Vlastimil Babka Cc: Wei Yang Cc: Yang Shi Signed-off-by: Andrew Morton --- mm/huge_memory.c | 25 +++++++++++++------------ 1 file changed, 13 insertions(+), 12 deletions(-) --- a/mm/huge_memory.c~mm-thp-narrow-lru-locking +++ a/mm/huge_memory.c @@ -2446,7 +2446,7 @@ static void __split_huge_page_tail(struc } =20 static void __split_huge_page(struct page *page, struct list_head *list, - pgoff_t end, unsigned long flags) + pgoff_t end) { struct page *head =3D compound_head(page); pg_data_t *pgdat =3D page_pgdat(head); @@ -2456,8 +2456,6 @@ static void __split_huge_page(struct pag unsigned int nr =3D thp_nr_pages(head); int i; =20 - lruvec =3D mem_cgroup_page_lruvec(head, pgdat); - /* complete memcg works before add pages to LRU */ mem_cgroup_split_huge_fixup(head); =20 @@ -2469,6 +2467,11 @@ static void __split_huge_page(struct pag xa_lock(&swap_cache->i_pages); } =20 + /* prevent PageLRU to go away from under us, and freeze lru stats */ + spin_lock(&pgdat->lru_lock); + + lruvec =3D mem_cgroup_page_lruvec(head, pgdat); + for (i =3D nr - 1; i >=3D 1; i--) { __split_huge_page_tail(head, i, lruvec, list); /* Some pages can be beyond i_size: drop them from page cache */ @@ -2488,6 +2491,8 @@ static void __split_huge_page(struct pag } =20 ClearPageCompound(head); + spin_unlock(&pgdat->lru_lock); + /* Caller disabled irqs, so they are still disabled here */ =20 split_page_owner(head, nr); =20 @@ -2505,8 +2510,7 @@ static void __split_huge_page(struct pag page_ref_add(head, 2); xa_unlock(&head->mapping->i_pages); } - - spin_unlock_irqrestore(&pgdat->lru_lock, flags); + local_irq_enable(); =20 remap_page(head, nr); =20 @@ -2652,12 +2656,10 @@ bool can_split_huge_page(struct page *pa int split_huge_page_to_list(struct page *page, struct list_head *list) { struct page *head =3D compound_head(page); - struct pglist_data *pgdata =3D NODE_DATA(page_to_nid(head)); struct deferred_split *ds_queue =3D get_deferred_split_queue(head); struct anon_vma *anon_vma =3D NULL; struct address_space *mapping =3D NULL; int count, mapcount, extra_pins, ret; - unsigned long flags; pgoff_t end; =20 VM_BUG_ON_PAGE(is_huge_zero_page(head), head); @@ -2718,9 +2720,8 @@ int split_huge_page_to_list(struct page unmap_page(head); VM_BUG_ON_PAGE(compound_mapcount(head), head); =20 - /* prevent PageLRU to go away from under us, and freeze lru stats */ - spin_lock_irqsave(&pgdata->lru_lock, flags); - + /* block interrupt reentry in xa_lock and spinlock */ + local_irq_disable(); if (mapping) { XA_STATE(xas, &mapping->i_pages, page_index(head)); =20 @@ -2750,7 +2751,7 @@ int split_huge_page_to_list(struct page __dec_lruvec_page_state(head, NR_FILE_THPS); } =20 - __split_huge_page(page, list, end, flags); + __split_huge_page(page, list, end); ret =3D 0; } else { if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) { @@ -2764,7 +2765,7 @@ int split_huge_page_to_list(struct page spin_unlock(&ds_queue->split_queue_lock); fail: if (mapping) xa_unlock(&mapping->i_pages); - spin_unlock_irqrestore(&pgdata->lru_lock, flags); + local_irq_enable(); remap_page(head, thp_nr_pages(head)); ret =3D -EBUSY; } _