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 B0C28C2BA19 for ; Wed, 15 Apr 2020 20:31:44 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6D73720774 for ; Wed, 15 Apr 2020 20:31:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6D73720774 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 038E98E003F; Wed, 15 Apr 2020 16:31:44 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id F2BF78E0001; Wed, 15 Apr 2020 16:31:43 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E41618E003F; Wed, 15 Apr 2020 16:31:43 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0250.hostedemail.com [216.40.44.250]) by kanga.kvack.org (Postfix) with ESMTP id CC9168E0001 for ; Wed, 15 Apr 2020 16:31:43 -0400 (EDT) Received: from smtpin29.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 8F1D140D3 for ; Wed, 15 Apr 2020 20:31:43 +0000 (UTC) X-FDA: 76711235286.29.voice32_6643eec2a0f1d X-HE-Tag: voice32_6643eec2a0f1d X-Filterd-Recvd-Size: 5220 Received: from out30-44.freemail.mail.aliyun.com (out30-44.freemail.mail.aliyun.com [115.124.30.44]) by imf40.hostedemail.com (Postfix) with ESMTP for ; Wed, 15 Apr 2020 20:31:42 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R201e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07484;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=9;SR=0;TI=SMTPD_---0TvdzT39_1586982696; Received: from US-143344MP.local(mailfrom:yang.shi@linux.alibaba.com fp:SMTPD_---0TvdzT39_1586982696) by smtp.aliyun-inc.com(127.0.0.1); Thu, 16 Apr 2020 04:31:39 +0800 Subject: Re: [PATCHv3, RESEND 2/8] khugepaged: Do not stop collapse if less than half PTEs are referenced To: "Kirill A. Shutemov" , akpm@linux-foundation.org, Andrea Arcangeli Cc: Zi Yan , Ralph Campbell , John Hubbard , William Kucharski , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20200413125220.663-1-kirill.shutemov@linux.intel.com> <20200413125220.663-3-kirill.shutemov@linux.intel.com> From: Yang Shi Message-ID: <902cad73-c3ef-c274-7483-c948167639e9@linux.alibaba.com> Date: Wed, 15 Apr 2020 13:31:33 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20200413125220.663-3-kirill.shutemov@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US 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: On 4/13/20 5:52 AM, Kirill A. Shutemov wrote: > __collapse_huge_page_swapin() checks the number of referenced PTE to > decide if the memory range is hot enough to justify swapin. > > We have few problems with the approach: > > - It is way too late: we can do the check much earlier and safe time. > khugepaged_scan_pmd() already knows if we have any pages to swap in > and number of referenced page. > > - It stops collapse altogether if there's not enough referenced pages, > not only swappingin. > > Fix it by making the right check early. We also can avoid additional > page table scanning if khugepaged_scan_pmd() haven't found any swap > entries. > > Signed-off-by: Kirill A. Shutemov > Fixes: 0db501f7a34c ("mm, thp: convert from optimistic swapin collapsing to conservative") > --- > mm/khugepaged.c | 25 ++++++++++--------------- > 1 file changed, 10 insertions(+), 15 deletions(-) Acked-by: Yang Shi Just a nit below. > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 99bab7e4d05b..5968ec5ddd6b 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -902,11 +902,6 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, > .pgoff = linear_page_index(vma, address), > }; > > - /* we only decide to swapin, if there is enough young ptes */ > - if (referenced < HPAGE_PMD_NR/2) { > - trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); > - return false; > - } > vmf.pte = pte_offset_map(pmd, address); > for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE; > vmf.pte++, vmf.address += PAGE_SIZE) { > @@ -946,7 +941,7 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, > static void collapse_huge_page(struct mm_struct *mm, > unsigned long address, > struct page **hpage, > - int node, int referenced) > + int node, int referenced, int unmapped) > { > pmd_t *pmd, _pmd; > pte_t *pte; > @@ -1003,7 +998,8 @@ static void collapse_huge_page(struct mm_struct *mm, > * If it fails, we release mmap_sem and jump out_nolock. > * Continuing to collapse causes inconsistency. > */ > - if (!__collapse_huge_page_swapin(mm, vma, address, pmd, referenced)) { > + if (unmapped && !__collapse_huge_page_swapin(mm, vma, address, > + pmd, referenced)) { > mem_cgroup_cancel_charge(new_page, memcg, true); > up_read(&mm->mmap_sem); > goto out_nolock; > @@ -1214,22 +1210,21 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, > mmu_notifier_test_young(vma->vm_mm, address)) > referenced++; > } > - if (writable) { > - if (referenced) { > + if (!writable) { > + result = SCAN_PAGE_RO; > + } else if (!referenced || (unmapped && referenced < HPAGE_PMD_NR/2)) { > + result = SCAN_LACK_REFERENCED_PAGE; > + } else { > result = SCAN_SUCCEED; > ret = 1; Shall fix the indentation for the above two statements? > - } else { > - result = SCAN_LACK_REFERENCED_PAGE; > - } > - } else { > - result = SCAN_PAGE_RO; > } > out_unmap: > pte_unmap_unlock(pte, ptl); > if (ret) { > node = khugepaged_find_target_node(); > /* collapse_huge_page will return with the mmap_sem released */ > - collapse_huge_page(mm, address, hpage, node, referenced); > + collapse_huge_page(mm, address, hpage, node, > + referenced, unmapped); > } > out: > trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,