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=-9.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 6953DC32750 for ; Fri, 2 Aug 2019 23:18:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3EDC52087E for ; Fri, 2 Aug 2019 23:18:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="VkdmKG5i" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2437391AbfHBXSf (ORCPT ); Fri, 2 Aug 2019 19:18:35 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:30716 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2437351AbfHBXS2 (ORCPT ); Fri, 2 Aug 2019 19:18:28 -0400 Received: from pps.filterd (m0001255.ppops.net [127.0.0.1]) by mx0b-00082601.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x72NGxUv012398 for ; Fri, 2 Aug 2019 16:18:26 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-type; s=facebook; bh=QnDZR2Atc3IvSm/9hGSkzUy/OPiqYnHl0bzsO+otMxg=; b=VkdmKG5iVKHe5uUBb8vFGrVhSdnMe3Q1pRvmnwVW/KrS/qpTafzadphPnLxgddiNh1P2 ZBNF93tRgqsLBhqLybEmN0deOE208q7UTeyrPnZjJiAXH4UXa6/kA5msPCzOz+iCEMdS HHQZRgOKULNq9E8rNEoo5ZtL6Pv+4yz8IPI= Received: from mail.thefacebook.com (mailout.thefacebook.com [199.201.64.23]) by mx0b-00082601.pphosted.com with ESMTP id 2u4s4q18aj-9 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-SHA384 bits=256 verify=NOT) for ; Fri, 02 Aug 2019 16:18:26 -0700 Received: from mx-out.facebook.com (2620:10d:c081:10::13) by mail.thefacebook.com (2620:10d:c081:35::125) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA) id 15.1.1713.5; Fri, 2 Aug 2019 16:18:25 -0700 Received: by devbig006.ftw2.facebook.com (Postfix, from userid 4523) id CA45362E2BEF; Fri, 2 Aug 2019 16:18:21 -0700 (PDT) Smtp-Origin-Hostprefix: devbig From: Song Liu Smtp-Origin-Hostname: devbig006.ftw2.facebook.com To: , , CC: , , , , , , Song Liu Smtp-Origin-Cluster: ftw2c04 Subject: [PATCH v4 1/2] khugepaged: enable collapse pmd for pte-mapped THP Date: Fri, 2 Aug 2019 16:18:16 -0700 Message-ID: <20190802231817.548920-2-songliubraving@fb.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190802231817.548920-1-songliubraving@fb.com> References: <20190802231817.548920-1-songliubraving@fb.com> X-FB-Internal: Safe MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-08-02_10:,, signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 malwarescore=0 suspectscore=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=549 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1908020241 X-FB-Internal: deliver Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org khugepaged needs exclusive mmap_sem to access page table. When it fails to lock mmap_sem, the page will fault in as pte-mapped THP. As the page is already a THP, khugepaged will not handle this pmd again. This patch enables the khugepaged to retry collapse the page table. struct mm_slot (in khugepaged.c) is extended with an array, containing addresses of pte-mapped THPs. We use array here for simplicity. We can easily replace it with more advanced data structures when needed. In khugepaged_scan_mm_slot(), if the mm contains pte-mapped THP, we try to collapse the page table. Since collapse may happen at an later time, some pages may already fault in. collapse_pte_mapped_thp() is added to properly handle these pages. collapse_pte_mapped_thp() also double checks whether all ptes in this pmd are mapping to the same THP. This is necessary because some subpage of the THP may be replaced, for example by uprobe. In such cases, it is not possible to collapse the pmd. Acked-by: Kirill A. Shutemov Cc: Oleg Nesterov Signed-off-by: Song Liu --- include/linux/khugepaged.h | 12 ++++ mm/khugepaged.c | 123 ++++++++++++++++++++++++++++++++++++- 2 files changed, 134 insertions(+), 1 deletion(-) diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h index 082d1d2a5216..bc45ea1efbf7 100644 --- a/include/linux/khugepaged.h +++ b/include/linux/khugepaged.h @@ -15,6 +15,14 @@ extern int __khugepaged_enter(struct mm_struct *mm); extern void __khugepaged_exit(struct mm_struct *mm); extern int khugepaged_enter_vma_merge(struct vm_area_struct *vma, unsigned long vm_flags); +#ifdef CONFIG_SHMEM +extern void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr); +#else +static inline void collapse_pte_mapped_thp(struct mm_struct *mm, + unsigned long addr) +{ +} +#endif #define khugepaged_enabled() \ (transparent_hugepage_flags & \ @@ -73,6 +81,10 @@ static inline int khugepaged_enter_vma_merge(struct vm_area_struct *vma, { return 0; } +static inline void collapse_pte_mapped_thp(struct mm_struct *mm, + unsigned long addr) +{ +} #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ #endif /* _LINUX_KHUGEPAGED_H */ diff --git a/mm/khugepaged.c b/mm/khugepaged.c index eaaa21b23215..ba36ff5c1d82 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -76,6 +76,8 @@ static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); static struct kmem_cache *mm_slot_cache __read_mostly; +#define MAX_PTE_MAPPED_THP 8 + /** * struct mm_slot - hash lookup from mm to mm_slot * @hash: hash collision list @@ -86,6 +88,10 @@ struct mm_slot { struct hlist_node hash; struct list_head mm_node; struct mm_struct *mm; + + /* pte-mapped THP in this mm */ + int nr_pte_mapped_thp; + unsigned long pte_mapped_thp[MAX_PTE_MAPPED_THP]; }; /** @@ -1248,6 +1254,119 @@ static void collect_mm_slot(struct mm_slot *mm_slot) } #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE) +/* + * Notify khugepaged that given addr of the mm is pte-mapped THP. Then + * khugepaged should try to collapse the page table. + */ +static int khugepaged_add_pte_mapped_thp(struct mm_struct *mm, + unsigned long addr) +{ + struct mm_slot *mm_slot; + + VM_BUG_ON(addr & ~HPAGE_PMD_MASK); + + spin_lock(&khugepaged_mm_lock); + mm_slot = get_mm_slot(mm); + if (likely(mm_slot && mm_slot->nr_pte_mapped_thp < MAX_PTE_MAPPED_THP)) + mm_slot->pte_mapped_thp[mm_slot->nr_pte_mapped_thp++] = addr; + spin_unlock(&khugepaged_mm_lock); + return 0; +} + +/** + * Try to collapse a pte-mapped THP for mm at address haddr. + * + * This function checks whether all the PTEs in the PMD are pointing to the + * right THP. If so, retract the page table so the THP can refault in with + * as pmd-mapped. + */ +void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr) +{ + unsigned long haddr = addr & HPAGE_PMD_MASK; + struct vm_area_struct *vma = find_vma(mm, haddr); + pmd_t *pmd = mm_find_pmd(mm, haddr); + struct page *hpage = NULL; + spinlock_t *ptl; + int count = 0; + pmd_t _pmd; + int i; + + if (!vma || !vma->vm_file || !pmd || + vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE) + return; + + /* step 1: check all mapped PTEs are to the right huge page */ + for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) { + pte_t *pte = pte_offset_map(pmd, addr); + struct page *page; + + if (pte_none(*pte)) + continue; + + page = vm_normal_page(vma, addr, *pte); + + if (!page || !PageCompound(page)) + return; + + if (!hpage) { + hpage = compound_head(page); + if (hpage->mapping != vma->vm_file->f_mapping) + return; + } + + if (hpage + i != page) + return; + count++; + } + + /* step 2: adjust rmap */ + for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) { + pte_t *pte = pte_offset_map(pmd, addr); + struct page *page; + + if (pte_none(*pte)) + continue; + page = vm_normal_page(vma, addr, *pte); + page_remove_rmap(page, false); + } + + /* step 3: set proper refcount and mm_counters. */ + if (hpage) { + page_ref_sub(hpage, count); + add_mm_counter(vma->vm_mm, mm_counter_file(hpage), -count); + } + + /* step 4: collapse pmd */ + ptl = pmd_lock(vma->vm_mm, pmd); + _pmd = pmdp_collapse_flush(vma, addr, pmd); + spin_unlock(ptl); + mm_dec_nr_ptes(mm); + pte_free(mm, pmd_pgtable(_pmd)); +} + +static int khugepaged_collapse_pte_mapped_thps(struct mm_slot *mm_slot) +{ + struct mm_struct *mm = mm_slot->mm; + int i; + + if (likely(mm_slot->nr_pte_mapped_thp == 0)) + return 0; + + if (!down_write_trylock(&mm->mmap_sem)) + return -EBUSY; + + if (unlikely(khugepaged_test_exit(mm))) + goto out; + + for (i = 0; i < mm_slot->nr_pte_mapped_thp; i++) + collapse_pte_mapped_thp(mm, mm_slot->pte_mapped_thp[i]); + +out: + mm_slot->nr_pte_mapped_thp = 0; + up_write(&mm->mmap_sem); + return 0; +} + static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) { struct vm_area_struct *vma; @@ -1281,7 +1400,8 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) up_write(&vma->vm_mm->mmap_sem); mm_dec_nr_ptes(vma->vm_mm); pte_free(vma->vm_mm, pmd_pgtable(_pmd)); - } + } else + khugepaged_add_pte_mapped_thp(vma->vm_mm, addr); } i_mmap_unlock_write(mapping); } @@ -1668,6 +1788,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, khugepaged_scan.mm_slot = mm_slot; } spin_unlock(&khugepaged_mm_lock); + khugepaged_collapse_pte_mapped_thps(mm_slot); mm = mm_slot->mm; /* -- 2.17.1