From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: + mm-add-vm_insert_pages.patch added to -mm tree Date: Wed, 12 Feb 2020 18:56:57 -0800 Message-ID: <20200213025657.SqK-UkL58%akpm@linux-foundation.org> References: <20200203173311.6269a8be06a05e5a4aa08a93@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.29.99]:39312 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729432AbgBMC46 (ORCPT ); Wed, 12 Feb 2020 21:56:58 -0500 In-Reply-To: <20200203173311.6269a8be06a05e5a4aa08a93@linux-foundation.org> Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: arjunroy@google.com, davem@davemloft.net, edumazet@google.com, mm-commits@vger.kernel.org, soheil@google.com The patch titled Subject: mm/memory.c: add vm_insert_pages() has been added to the -mm tree. Its filename is mm-add-vm_insert_pages.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mm-add-vm_insert_pages.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/mm-add-vm_insert_pages.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Arjun Roy Subject: mm/memory.c: add vm_insert_pages() Add the ability to insert multiple pages at once to a user VM with lower PTE spinlock operations. The intention of this patch-set is to reduce atomic ops for tcp zerocopy receives, which normally hits the same spinlock multiple times consecutively. Link: http://lkml.kernel.org/r/20200128025958.43490-2-arjunroy.kdev@gmail.com Signed-off-by: Arjun Roy Signed-off-by: Eric Dumazet Signed-off-by: Soheil Hassas Yeganeh Cc: David Miller Signed-off-by: Andrew Morton --- include/linux/mm.h | 2 mm/memory.c | 111 ++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 111 insertions(+), 2 deletions(-) --- a/include/linux/mm.h~mm-add-vm_insert_pages +++ a/include/linux/mm.h @@ -2597,6 +2597,8 @@ struct vm_area_struct *find_extend_vma(s int remap_pfn_range(struct vm_area_struct *, unsigned long addr, unsigned long pfn, unsigned long size, pgprot_t); int vm_insert_page(struct vm_area_struct *, unsigned long addr, struct page *); +int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr, + struct page **pages, unsigned long *num); int vm_map_pages(struct vm_area_struct *vma, struct page **pages, unsigned long num); int vm_map_pages_zero(struct vm_area_struct *vma, struct page **pages, --- a/mm/memory.c~mm-add-vm_insert_pages +++ a/mm/memory.c @@ -1407,8 +1407,7 @@ void zap_vma_ptes(struct vm_area_struct } EXPORT_SYMBOL_GPL(zap_vma_ptes); -pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr, - spinlock_t **ptl) +static pmd_t *walk_to_pmd(struct mm_struct *mm, unsigned long addr) { pgd_t *pgd; p4d_t *p4d; @@ -1427,6 +1426,16 @@ pte_t *__get_locked_pte(struct mm_struct return NULL; VM_BUG_ON(pmd_trans_huge(*pmd)); + return pmd; +} + +pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr, + spinlock_t **ptl) +{ + pmd_t *pmd = walk_to_pmd(mm, addr); + + if (!pmd) + return NULL; return pte_alloc_map_lock(mm, pmd, addr, ptl); } @@ -1451,6 +1460,15 @@ static int insert_page_into_pte_locked(s return 0; } +static int insert_page_in_batch_locked(struct mm_struct *mm, pmd_t *pmd, + unsigned long addr, struct page *page, pgprot_t prot) +{ + const int err = validate_page_before_insert(page); + + return err ? err : insert_page_into_pte_locked( + mm, pte_offset_map(pmd, addr), addr, page, prot); +} + /* * This is the old fallback for page remapping. * @@ -1479,6 +1497,95 @@ out: return retval; } +/* insert_pages() amortizes the cost of spinlock operations + * when inserting pages in a loop. + */ +static int insert_pages(struct vm_area_struct *vma, unsigned long addr, + struct page **pages, unsigned long *num, pgprot_t prot) +{ + pmd_t *pmd = NULL; + spinlock_t *pte_lock = NULL; + struct mm_struct *const mm = vma->vm_mm; + unsigned long curr_page_idx = 0; + unsigned long remaining_pages_total = *num; + unsigned long pages_to_write_in_pmd; + int ret; +more: + ret = -EFAULT; + pmd = walk_to_pmd(mm, addr); + if (!pmd) + goto out; + + pages_to_write_in_pmd = min_t(unsigned long, + remaining_pages_total, PTRS_PER_PTE - pte_index(addr)); + + /* Allocate the PTE if necessary; takes PMD lock once only. */ + ret = -ENOMEM; + if (pte_alloc(mm, pmd, addr)) + goto out; + pte_lock = pte_lockptr(mm, pmd); + + while (pages_to_write_in_pmd) { + int pte_idx = 0; + const int batch_size = min_t(int, pages_to_write_in_pmd, 8); + + spin_lock(pte_lock); + for (; pte_idx < batch_size; ++pte_idx) { + int err = insert_page_in_batch_locked(mm, pmd, + addr, pages[curr_page_idx], prot); + if (unlikely(err)) { + spin_unlock(pte_lock); + ret = err; + remaining_pages_total -= pte_idx; + goto out; + } + addr += PAGE_SIZE; + ++curr_page_idx; + } + spin_unlock(pte_lock); + pages_to_write_in_pmd -= batch_size; + remaining_pages_total -= batch_size; + } + if (remaining_pages_total) + goto more; + ret = 0; +out: + *num = remaining_pages_total; + return ret; +} + +/** + * vm_insert_pages - insert multiple pages into user vma, batching the pmd lock. + * @vma: user vma to map to + * @addr: target start user address of these pages + * @pages: source kernel pages + * @num: in: number of pages to map. out: number of pages that were *not* + * mapped. (0 means all pages were successfully mapped). + * + * Preferred over vm_insert_page() when inserting multiple pages. + * + * In case of error, we may have mapped a subset of the provided + * pages. It is the caller's responsibility to account for this case. + * + * The same restrictions apply as in vm_insert_page(). + */ +int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr, + struct page **pages, unsigned long *num) +{ + const unsigned long end_addr = addr + (*num * PAGE_SIZE) - 1; + + if (addr < vma->vm_start || end_addr >= vma->vm_end) + return -EFAULT; + if (!(vma->vm_flags & VM_MIXEDMAP)) { + BUG_ON(down_read_trylock(&vma->vm_mm->mmap_sem)); + BUG_ON(vma->vm_flags & VM_PFNMAP); + vma->vm_flags |= VM_MIXEDMAP; + } + /* Defer page refcount checking till we're about to map that page. */ + return insert_pages(vma, addr, pages, num, vma->vm_page_prot); +} +EXPORT_SYMBOL(vm_insert_pages); + /** * vm_insert_page - insert single page into user vma * @vma: user vma to map to _ Patches currently in -mm which might be from arjunroy@google.com are mm-refactor-insert_page-to-prepare-for-batched-lock-insert.patch mm-add-vm_insert_pages.patch net-zerocopy-use-vm_insert_pages-for-tcp-rcv-zerocopy.patch