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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,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 1C4A7C433DF for ; Mon, 6 Jul 2020 09:15:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 039D8206F5 for ; Mon, 6 Jul 2020 09:15:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728350AbgGFJPn (ORCPT ); Mon, 6 Jul 2020 05:15:43 -0400 Received: from out30-131.freemail.mail.aliyun.com ([115.124.30.131]:53869 "EHLO out30-131.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728024AbgGFJPn (ORCPT ); Mon, 6 Jul 2020 05:15:43 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R331e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04357;MF=alex.shi@linux.alibaba.com;NM=1;PH=DS;RN=16;SR=0;TI=SMTPD_---0U1sNi0q_1594026936; Received: from IT-FVFX43SYHV2H.local(mailfrom:alex.shi@linux.alibaba.com fp:SMTPD_---0U1sNi0q_1594026936) by smtp.aliyun-inc.com(127.0.0.1); Mon, 06 Jul 2020 17:15:36 +0800 Subject: Re: [PATCH v14 07/20] mm/thp: narrow lru locking From: Alex Shi To: akpm@linux-foundation.org, mgorman@techsingularity.net, tj@kernel.org, hughd@google.com, khlebnikov@yandex-team.ru, daniel.m.jordan@oracle.com, yang.shi@linux.alibaba.com, willy@infradead.org, hannes@cmpxchg.org, lkp@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, shakeelb@google.com, iamjoonsoo.kim@lge.com, richard.weiyang@gmail.com References: <1593752873-4493-1-git-send-email-alex.shi@linux.alibaba.com> <1593752873-4493-8-git-send-email-alex.shi@linux.alibaba.com> Message-ID: <124eeef1-ff2b-609e-3bf6-a118100c3f2a@linux.alibaba.com> Date: Mon, 6 Jul 2020 17:15:09 +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: <1593752873-4493-8-git-send-email-alex.shi@linux.alibaba.com> Content-Type: text/plain; charset=gbk Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Kirill & Johannes & Matthew, Would you like to give some comments or share your concern of this patchset, specialy for THP part? Many Thanks Alex ÔÚ 2020/7/3 ÏÂÎç1:07, Alex Shi дµÀ: > lru_lock and page cache xa_lock have no reason with current sequence, > put them together isn't necessary. let's narrow the lru locking, but > left the local_irq_disable to block interrupt re-entry and statistic update. > > 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(). > > Signed-off-by: Alex Shi > Signed-off-by: Wei Yang > Cc: Hugh Dickins > Cc: Kirill A. Shutemov > Cc: Andrea Arcangeli > Cc: Johannes Weiner > Cc: Matthew Wilcox > Cc: Andrew Morton > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > --- > mm/huge_memory.c | 24 ++++++++++++------------ > 1 file changed, 12 insertions(+), 12 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index b18f21da4dac..607869330329 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2433,7 +2433,7 @@ static void __split_huge_page_tail(struct page *head, int tail, > } > > static void __split_huge_page(struct page *page, struct list_head *list, > - pgoff_t end, unsigned long flags) > + pgoff_t end) > { > struct page *head = compound_head(page); > pg_data_t *pgdat = page_pgdat(head); > @@ -2442,8 +2442,6 @@ static void __split_huge_page(struct page *page, struct list_head *list, > unsigned long offset = 0; > int i; > > - lruvec = mem_cgroup_page_lruvec(head, pgdat); > - > /* complete memcg works before add pages to LRU */ > mem_cgroup_split_huge_fixup(head); > > @@ -2455,6 +2453,11 @@ static void __split_huge_page(struct page *page, struct list_head *list, > xa_lock(&swap_cache->i_pages); > } > > + /* lock lru list/PageCompound, ref freezed by page_ref_freeze */ > + spin_lock(&pgdat->lru_lock); > + > + lruvec = mem_cgroup_page_lruvec(head, pgdat); > + > for (i = HPAGE_PMD_NR - 1; i >= 1; i--) { > __split_huge_page_tail(head, i, lruvec, list); > /* Some pages can be beyond i_size: drop them from page cache */ > @@ -2474,6 +2477,8 @@ static void __split_huge_page(struct page *page, struct list_head *list, > } > > ClearPageCompound(head); > + spin_unlock(&pgdat->lru_lock); > + /* Caller disabled irqs, so they are still disabled here */ > > split_page_owner(head, HPAGE_PMD_ORDER); > > @@ -2491,8 +2496,7 @@ static void __split_huge_page(struct page *page, struct list_head *list, > page_ref_add(head, 2); > xa_unlock(&head->mapping->i_pages); > } > - > - spin_unlock_irqrestore(&pgdat->lru_lock, flags); > + local_irq_enable(); > > remap_page(head); > > @@ -2631,12 +2635,10 @@ bool can_split_huge_page(struct page *page, int *pextra_pins) > int split_huge_page_to_list(struct page *page, struct list_head *list) > { > struct page *head = compound_head(page); > - struct pglist_data *pgdata = NODE_DATA(page_to_nid(head)); > struct deferred_split *ds_queue = get_deferred_split_queue(head); > struct anon_vma *anon_vma = NULL; > struct address_space *mapping = NULL; > int count, mapcount, extra_pins, ret; > - unsigned long flags; > pgoff_t end; > > VM_BUG_ON_PAGE(is_huge_zero_page(head), head); > @@ -2697,9 +2699,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) > unmap_page(head); > VM_BUG_ON_PAGE(compound_mapcount(head), head); > > - /* prevent PageLRU to go away from under us, and freeze lru stats */ > - spin_lock_irqsave(&pgdata->lru_lock, flags); > - > + local_irq_disable(); > if (mapping) { > XA_STATE(xas, &mapping->i_pages, page_index(head)); > > @@ -2729,7 +2729,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) > __dec_node_page_state(head, NR_FILE_THPS); > } > > - __split_huge_page(page, list, end, flags); > + __split_huge_page(page, list, end); > if (PageSwapCache(head)) { > swp_entry_t entry = { .val = page_private(head) }; > > @@ -2748,7 +2748,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) > 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); > ret = -EBUSY; > } >