Received: by 2002:a05:7412:d1aa:b0:fc:a2b0:25d7 with SMTP id ba42csp363779rdb; Mon, 29 Jan 2024 04:53:29 -0800 (PST) X-Google-Smtp-Source: AGHT+IF15Nr9qfoaKm1HbMT2h/0teUP/Od9oSMyEY3m9/ZY0DloRQj0CMSEIDPiTSJeT2IfNsZ+y X-Received: by 2002:a05:651c:1507:b0:2cf:1977:d098 with SMTP id e7-20020a05651c150700b002cf1977d098mr3938341ljf.40.1706532808954; Mon, 29 Jan 2024 04:53:28 -0800 (PST) ARC-Seal: i=2; a=rsa-sha256; t=1706532808; cv=pass; d=google.com; s=arc-20160816; b=QlPpwT1ldF3zlRnH9izy+M8ONh3Sr2x94jrjcXmagG+NKTPaRgQuIH7dIj6+RdHDNI JRKiImqZhuFz2VKZniDt15aEA0au+8+ftaBgSV9kkMrU79/TlI3c53zysAERbHImC3Wr 2cZAyeCe/2vMBArnA65pUl59Nu5HAq4Cl9vfRsPgJXltTfUE5GRu9zRzo4x7ILdNX7r0 LxG7pk1rUMVGDAQQTLYzKrp4BuRYpQYe+F1FiztraASlkDWqFlOD3O3WN971MiWCi/rG eOOqfewqGy/b7LDUVwt35hu0U1P/7v20WEkLTFvA4b0UvNoX8CFqZDlGI7S9cJwnjshm 4tKw== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:mime-version:list-unsubscribe :list-subscribe:list-id:precedence:references:in-reply-to:message-id :date:subject:cc:to:from:dkim-signature; bh=GLdn+T1R5PiYDW19VyAaeLNlt8B1zt8mn8YsDhIt5B8=; fh=lZsZCQsH4ia1jFJuQK1Gi3cXLvdnrj+ub8bSs7lwlcw=; b=BgWt2oFFgezOs2jIvLc4lWwPtRTtMNaFAPIXeZVKcA+kfBFuh4ihhfUcpmpwOdjRe7 I0NpkCfNGwU8G40dQ4kkCvJZiZ/y6Ec/4+W0qF3v+llIO3DKnpgJIEwxDRBTPyawTGxQ J7wKuAaSXtTD9K9iV1TxP81QOoA9q7i1tZQSUIziIrZ+S/f3hl8rHfdcHFI/cK2HrGmO +hFh+cpAvHyijgrQUs8FFgFyTDF2sPgkir73wv4rthJIj8BG8rRnBCrWwrSfo0tbLyGI TENSVfE8GnzILNjG8AQnqPdZ4X4AKal/tJjwX8luwl192gtj51nDejZf4v6uBwP/igiO A+Pg== ARC-Authentication-Results: i=2; mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=SmzgwHJ1; arc=pass (i=1 spf=pass spfdomain=redhat.com dkim=pass dkdomain=redhat.com dmarc=pass fromdomain=redhat.com); spf=pass (google.com: domain of linux-kernel+bounces-42727-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) smtp.mailfrom="linux-kernel+bounces-42727-linux.lists.archive=gmail.com@vger.kernel.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Return-Path: Received: from am.mirrors.kernel.org (am.mirrors.kernel.org. [2604:1380:4601:e00::3]) by mx.google.com with ESMTPS id i29-20020a50d75d000000b0055f1d481e4fsi267740edj.28.2024.01.29.04.53.28 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 29 Jan 2024 04:53:28 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel+bounces-42727-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=SmzgwHJ1; arc=pass (i=1 spf=pass spfdomain=redhat.com dkim=pass dkdomain=redhat.com dmarc=pass fromdomain=redhat.com); spf=pass (google.com: domain of linux-kernel+bounces-42727-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) smtp.mailfrom="linux-kernel+bounces-42727-linux.lists.archive=gmail.com@vger.kernel.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by am.mirrors.kernel.org (Postfix) with ESMTPS id 882361F242E6 for ; Mon, 29 Jan 2024 12:53:28 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 74D38651B7; Mon, 29 Jan 2024 12:48:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="SmzgwHJ1" Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 84EDC651B5 for ; Mon, 29 Jan 2024 12:48:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706532502; cv=none; b=i4Dw8Z3vYH6P06xo5Wyka7MEpXdHlvoTljFNKxGaeDgNfpJwpgxkn3moyQw3wv9FXWO9+pv+M/I7OEgdA7OVCWsUdarV/f1gHyE8wy9wpPvyLlplBos0AxP9Uby+I10DjQU+DCJYKt16XAPVJj5SL+dTbpxdIa2RDCLL0CAFCfA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706532502; c=relaxed/simple; bh=BW1US5cMUO+3az2nkBk/Q2XXA2/iI656D4HsRTKejWY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=i90CLF45/cT7uJfKrjjqsicCy5fHsOLXPX/ARfhnkGjR17ksQCWQ8sPR6/N45+KJqUr5Rn/fGWD5B1ygLpYZgvvUODip9hUk9BHK+uYWG1lWp6aqneoXihBOOb9Yuv1LMR/NWosIQ+quu7+CTNlJR13mjOvnZt4K0fOjsX/uGmQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=SmzgwHJ1; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1706532499; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=GLdn+T1R5PiYDW19VyAaeLNlt8B1zt8mn8YsDhIt5B8=; b=SmzgwHJ1XT60HCh60HP2Q68+1dzGgv20haSbIjHNuN0GgCTH1FXhgvEBH0d8f7IQ+B2Tkl SyZHwh5TculXYfZt3cRnrGEoCixz3Y7eE1ltQ6OAK20FtuLgd4xSDHIgOA5+frLc49A3MO tbkgcJXkjk9rX6orJo8W/He+hI3n/18= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-602-1IZZ7hGdOwG8M8ciVMufmA-1; Mon, 29 Jan 2024 07:48:16 -0500 X-MC-Unique: 1IZZ7hGdOwG8M8ciVMufmA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 9B83A29AA3AC; Mon, 29 Jan 2024 12:48:14 +0000 (UTC) Received: from t14s.fritz.box (unknown [10.39.194.46]) by smtp.corp.redhat.com (Postfix) with ESMTP id 277D3111E8; Mon, 29 Jan 2024 12:48:09 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, David Hildenbrand , Andrew Morton , Matthew Wilcox , Ryan Roberts , Russell King , Catalin Marinas , Will Deacon , Dinh Nguyen , Michael Ellerman , Nicholas Piggin , Christophe Leroy , "Aneesh Kumar K.V" , "Naveen N. Rao" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , "David S. Miller" , linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org Subject: [PATCH v3 13/15] mm/memory: optimize fork() with PTE-mapped THP Date: Mon, 29 Jan 2024 13:46:47 +0100 Message-ID: <20240129124649.189745-14-david@redhat.com> In-Reply-To: <20240129124649.189745-1-david@redhat.com> References: <20240129124649.189745-1-david@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.5 Let's implement PTE batching when consecutive (present) PTEs map consecutive pages of the same large folio, and all other PTE bits besides the PFNs are equal. We will optimize folio_pte_batch() separately, to ignore selected PTE bits. This patch is based on work by Ryan Roberts. Use __always_inline for __copy_present_ptes() and keep the handling for single PTEs completely separate from the multi-PTE case: we really want the compiler to optimize for the single-PTE case with small folios, to not degrade performance. Note that PTE batching will never exceed a single page table and will always stay within VMA boundaries. Further, processing PTE-mapped THP that maybe pinned and have PageAnonExclusive set on at least one subpage should work as expected, but there is room for improvement: We will repeatedly (1) detect a PTE batch (2) detect that we have to copy a page (3) fall back and allocate a single page to copy a single page. For now we won't care as pinned pages are a corner case, and we should rather look into maintaining only a single PageAnonExclusive bit for large folios. Reviewed-by: Ryan Roberts Signed-off-by: David Hildenbrand --- include/linux/pgtable.h | 31 +++++++++++ mm/memory.c | 112 +++++++++++++++++++++++++++++++++------- 2 files changed, 124 insertions(+), 19 deletions(-) diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index 351cd9dc7194..aab227e12493 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -650,6 +650,37 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addres } #endif +#ifndef wrprotect_ptes +/** + * wrprotect_ptes - Write-protect PTEs that map consecutive pages of the same + * folio. + * @mm: Address space the pages are mapped into. + * @addr: Address the first page is mapped at. + * @ptep: Page table pointer for the first entry. + * @nr: Number of entries to write-protect. + * + * May be overridden by the architecture; otherwise, implemented as a simple + * loop over ptep_set_wrprotect(). + * + * Note that PTE bits in the PTE range besides the PFN can differ. For example, + * some PTEs might be write-protected. + * + * Context: The caller holds the page table lock. The PTEs map consecutive + * pages that belong to the same folio. The PTEs are all in the same PMD. + */ +static inline void wrprotect_ptes(struct mm_struct *mm, unsigned long addr, + pte_t *ptep, unsigned int nr) +{ + for (;;) { + ptep_set_wrprotect(mm, addr, ptep); + if (--nr == 0) + break; + ptep++; + addr += PAGE_SIZE; + } +} +#endif + /* * On some architectures hardware does not set page access bit when accessing * memory page, it is responsibility of software setting this bit. It brings diff --git a/mm/memory.c b/mm/memory.c index 41b24da5be38..86f8a0021c8e 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -930,15 +930,15 @@ copy_present_page(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma return 0; } -static inline void __copy_present_pte(struct vm_area_struct *dst_vma, +static __always_inline void __copy_present_ptes(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, pte_t *dst_pte, pte_t *src_pte, - pte_t pte, unsigned long addr) + pte_t pte, unsigned long addr, int nr) { struct mm_struct *src_mm = src_vma->vm_mm; /* If it's a COW mapping, write protect it both processes. */ if (is_cow_mapping(src_vma->vm_flags) && pte_write(pte)) { - ptep_set_wrprotect(src_mm, addr, src_pte); + wrprotect_ptes(src_mm, addr, src_pte, nr); pte = pte_wrprotect(pte); } @@ -950,26 +950,93 @@ static inline void __copy_present_pte(struct vm_area_struct *dst_vma, if (!userfaultfd_wp(dst_vma)) pte = pte_clear_uffd_wp(pte); - set_pte_at(dst_vma->vm_mm, addr, dst_pte, pte); + set_ptes(dst_vma->vm_mm, addr, dst_pte, pte, nr); +} + +/* + * Detect a PTE batch: consecutive (present) PTEs that map consecutive + * pages of the same folio. + * + * All PTEs inside a PTE batch have the same PTE bits set, excluding the PFN. + */ +static inline int folio_pte_batch(struct folio *folio, unsigned long addr, + pte_t *start_ptep, pte_t pte, int max_nr) +{ + unsigned long folio_end_pfn = folio_pfn(folio) + folio_nr_pages(folio); + const pte_t *end_ptep = start_ptep + max_nr; + pte_t expected_pte = pte_next_pfn(pte); + pte_t *ptep = start_ptep + 1; + + VM_WARN_ON_FOLIO(!pte_present(pte), folio); + + while (ptep != end_ptep) { + pte = ptep_get(ptep); + + if (!pte_same(pte, expected_pte)) + break; + + /* + * Stop immediately once we reached the end of the folio. In + * corner cases the next PFN might fall into a different + * folio. + */ + if (pte_pfn(pte) == folio_end_pfn) + break; + + expected_pte = pte_next_pfn(expected_pte); + ptep++; + } + + return ptep - start_ptep; } /* - * Copy one pte. Returns 0 if succeeded, or -EAGAIN if one preallocated page - * is required to copy this pte. + * Copy one present PTE, trying to batch-process subsequent PTEs that map + * consecutive pages of the same folio by copying them as well. + * + * Returns -EAGAIN if one preallocated page is required to copy the next PTE. + * Otherwise, returns the number of copied PTEs (at least 1). */ static inline int -copy_present_pte(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, +copy_present_ptes(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, pte_t *dst_pte, pte_t *src_pte, pte_t pte, unsigned long addr, - int *rss, struct folio **prealloc) + int max_nr, int *rss, struct folio **prealloc) { struct page *page; struct folio *folio; + int err, nr; page = vm_normal_page(src_vma, addr, pte); if (unlikely(!page)) goto copy_pte; folio = page_folio(page); + + /* + * If we likely have to copy, just don't bother with batching. Make + * sure that the common "small folio" case is as fast as possible + * by keeping the batching logic separate. + */ + if (unlikely(!*prealloc && folio_test_large(folio) && max_nr != 1)) { + nr = folio_pte_batch(folio, addr, src_pte, pte, max_nr); + folio_ref_add(folio, nr); + if (folio_test_anon(folio)) { + if (unlikely(folio_try_dup_anon_rmap_ptes(folio, page, + nr, src_vma))) { + folio_ref_sub(folio, nr); + return -EAGAIN; + } + rss[MM_ANONPAGES] += nr; + VM_WARN_ON_FOLIO(PageAnonExclusive(page), folio); + } else { + folio_dup_file_rmap_ptes(folio, page, nr); + rss[mm_counter_file(folio)] += nr; + } + __copy_present_ptes(dst_vma, src_vma, dst_pte, src_pte, pte, + addr, nr); + return nr; + } + folio_get(folio); if (folio_test_anon(folio)) { /* @@ -981,8 +1048,9 @@ copy_present_pte(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, if (unlikely(folio_try_dup_anon_rmap_pte(folio, page, src_vma))) { /* Page may be pinned, we have to copy. */ folio_put(folio); - return copy_present_page(dst_vma, src_vma, dst_pte, src_pte, - addr, rss, prealloc, page); + err = copy_present_page(dst_vma, src_vma, dst_pte, src_pte, + addr, rss, prealloc, page); + return err ? err : 1; } rss[MM_ANONPAGES]++; VM_WARN_ON_FOLIO(PageAnonExclusive(page), folio); @@ -992,8 +1060,8 @@ copy_present_pte(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, } copy_pte: - __copy_present_pte(dst_vma, src_vma, dst_pte, src_pte, pte, addr); - return 0; + __copy_present_ptes(dst_vma, src_vma, dst_pte, src_pte, pte, addr, 1); + return 1; } static inline struct folio *folio_prealloc(struct mm_struct *src_mm, @@ -1030,10 +1098,11 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, pte_t *src_pte, *dst_pte; pte_t ptent; spinlock_t *src_ptl, *dst_ptl; - int progress, ret = 0; + int progress, max_nr, ret = 0; int rss[NR_MM_COUNTERS]; swp_entry_t entry = (swp_entry_t){0}; struct folio *prealloc = NULL; + int nr; again: progress = 0; @@ -1064,6 +1133,8 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, arch_enter_lazy_mmu_mode(); do { + nr = 1; + /* * We are holding two locks at this point - either of them * could generate latencies in another task on another CPU. @@ -1100,9 +1171,10 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, */ WARN_ON_ONCE(ret != -ENOENT); } - /* copy_present_pte() will clear `*prealloc' if consumed */ - ret = copy_present_pte(dst_vma, src_vma, dst_pte, src_pte, - ptent, addr, rss, &prealloc); + /* copy_present_ptes() will clear `*prealloc' if consumed */ + max_nr = (end - addr) / PAGE_SIZE; + ret = copy_present_ptes(dst_vma, src_vma, dst_pte, src_pte, + ptent, addr, max_nr, rss, &prealloc); /* * If we need a pre-allocated page for this pte, drop the * locks, allocate, and try again. @@ -1119,8 +1191,10 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, folio_put(prealloc); prealloc = NULL; } - progress += 8; - } while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end); + nr = ret; + progress += 8 * nr; + } while (dst_pte += nr, src_pte += nr, addr += PAGE_SIZE * nr, + addr != end); arch_leave_lazy_mmu_mode(); pte_unmap_unlock(orig_src_pte, src_ptl); @@ -1141,7 +1215,7 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, prealloc = folio_prealloc(src_mm, src_vma, addr, false); if (!prealloc) return -ENOMEM; - } else if (ret) { + } else if (ret < 0) { VM_WARN_ON_ONCE(1); } -- 2.43.0