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Wed, 28 Jul 2021 20:07:48 +0000 Received: from BLAPR10MB4835.namprd10.prod.outlook.com ([fe80::5833:5ab2:944c:7360]) by BLAPR10MB4835.namprd10.prod.outlook.com ([fe80::5833:5ab2:944c:7360%9]) with mapi id 15.20.4373.020; Wed, 28 Jul 2021 20:07:48 +0000 Subject: Re: [PATCH v3 13/14] mm/gup: grab head page refcount once for group of subpages To: Dan Williams Cc: Linux MM , Vishal Verma , Dave Jiang , Naoya Horiguchi , Matthew Wilcox , Jason Gunthorpe , John Hubbard , Jane Chu , Muchun Song , Mike Kravetz , Andrew Morton , Jonathan Corbet , Linux NVDIMM , Linux Doc Mailing List References: <20210714193542.21857-1-joao.m.martins@oracle.com> <20210714193542.21857-14-joao.m.martins@oracle.com> From: Joao Martins Message-ID: <861f03ee-f8c8-cc89-3fc2-884c062fea11@oracle.com> Date: Wed, 28 Jul 2021 21:07:41 +0100 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: LO3P123CA0011.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:ba::16) To BLAPR10MB4835.namprd10.prod.outlook.com (2603:10b6:208:331::11) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [192.168.1.67] (94.61.1.144) by LO3P123CA0011.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:ba::16) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4373.18 via Frontend Transport; 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dkim=pass header.d=oracle.com header.s=corp-2021-07-09 header.b=Yem0q7eb; dkim=pass header.d=oracle.com header.s=corp-2020-01-29 header.b=fVy1FBuw; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b="mpX/es0W"; spf=none (imf28.hostedemail.com: domain of joao.m.martins@oracle.com has no SPF policy when checking 205.220.177.32) smtp.mailfrom=joao.m.martins@oracle.com; dmarc=pass (policy=none) header.from=oracle.com X-Stat-Signature: qewf5sh9m6jdz3dfm45xxs76jwoqf9eu X-HE-Tag: 1627502875-316619 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 7/28/21 8:55 PM, Dan Williams wrote: > On Wed, Jul 14, 2021 at 12:36 PM Joao Martins wrote: >> >> Use try_grab_compound_head() for device-dax GUP when configured with a >> compound pagemap. >> >> Rather than incrementing the refcount for each page, do one atomic >> addition for all the pages to be pinned. >> >> Performance measured by gup_benchmark improves considerably >> get_user_pages_fast() and pin_user_pages_fast() with NVDIMMs: >> >> $ gup_test -f /dev/dax1.0 -m 16384 -r 10 -S [-u,-a] -n 512 -w >> (get_user_pages_fast 2M pages) ~59 ms -> ~6.1 ms >> (pin_user_pages_fast 2M pages) ~87 ms -> ~6.2 ms >> [altmap] >> (get_user_pages_fast 2M pages) ~494 ms -> ~9 ms >> (pin_user_pages_fast 2M pages) ~494 ms -> ~10 ms >> >> $ gup_test -f /dev/dax1.0 -m 129022 -r 10 -S [-u,-a] -n 512 -w >> (get_user_pages_fast 2M pages) ~492 ms -> ~49 ms >> (pin_user_pages_fast 2M pages) ~493 ms -> ~50 ms >> [altmap with -m 127004] >> (get_user_pages_fast 2M pages) ~3.91 sec -> ~70 ms >> (pin_user_pages_fast 2M pages) ~3.97 sec -> ~74 ms >> >> Signed-off-by: Joao Martins >> --- >> mm/gup.c | 53 +++++++++++++++++++++++++++++++++-------------------- >> 1 file changed, 33 insertions(+), 20 deletions(-) >> >> diff --git a/mm/gup.c b/mm/gup.c >> index 42b8b1fa6521..9baaa1c0b7f3 100644 >> --- a/mm/gup.c >> +++ b/mm/gup.c >> @@ -2234,31 +2234,55 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, >> } >> #endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */ >> >> + >> +static int record_subpages(struct page *page, unsigned long addr, >> + unsigned long end, struct page **pages) >> +{ >> + int nr; >> + >> + for (nr = 0; addr != end; addr += PAGE_SIZE) >> + pages[nr++] = page++; >> + >> + return nr; >> +} >> + >> #if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE) >> static int __gup_device_huge(unsigned long pfn, unsigned long addr, >> unsigned long end, unsigned int flags, >> struct page **pages, int *nr) >> { >> - int nr_start = *nr; >> + int refs, nr_start = *nr; >> struct dev_pagemap *pgmap = NULL; >> >> do { >> - struct page *page = pfn_to_page(pfn); >> + struct page *pinned_head, *head, *page = pfn_to_page(pfn); >> + unsigned long next; >> >> pgmap = get_dev_pagemap(pfn, pgmap); >> if (unlikely(!pgmap)) { >> undo_dev_pagemap(nr, nr_start, flags, pages); >> return 0; >> } >> - SetPageReferenced(page); >> - pages[*nr] = page; >> - if (unlikely(!try_grab_page(page, flags))) { >> - undo_dev_pagemap(nr, nr_start, flags, pages); >> + >> + head = compound_head(page); >> + /* @end is assumed to be limited at most one compound page */ >> + next = PageCompound(head) ? end : addr + PAGE_SIZE; > > Please no ternary operator for this check, but otherwise this patch > looks good to me. > OK. I take that you prefer this instead: unsigned long next = addr + PAGE_SIZE; [...] /* @end is assumed to be limited at most one compound page */ if (PageCompound(head)) next = end; > Reviewed-by: Dan Williams > Thanks!