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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 1A91CC433E0 for ; Mon, 11 Jan 2021 10:31:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CB829225AC for ; Mon, 11 Jan 2021 10:31:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729113AbhAKKbH convert rfc822-to-8bit (ORCPT ); Mon, 11 Jan 2021 05:31:07 -0500 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.85.151]:23063 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728725AbhAKKbH (ORCPT ); Mon, 11 Jan 2021 05:31:07 -0500 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-34-7ibnZ-d1Oea7y-_CqhqRwQ-1; Mon, 11 Jan 2021 10:29:29 +0000 X-MC-Unique: 7ibnZ-d1Oea7y-_CqhqRwQ-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Mon, 11 Jan 2021 10:29:28 +0000 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Mon, 11 Jan 2021 10:29:28 +0000 From: David Laight To: 'Al Viro' , Mikulas Patocka CC: Andrew Morton , Dan Williams , Vishal Verma , "Dave Jiang" , Ira Weiny , "Matthew Wilcox" , Jan Kara , Steven Whitehouse , Eric Sandeen , Dave Chinner , Theodore Ts'o , Wang Jianchao , "Kani, Toshi" , "Norton, Scott J" , "Tadakamadla, Rajesh" , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-nvdimm@lists.01.org" Subject: RE: [RFC v2] nvfs: a filesystem for persistent memory Thread-Topic: [RFC v2] nvfs: a filesystem for persistent memory Thread-Index: AQHW52zcFLyucqAcQUmnqwhwPozPcaoiOfvQ Date: Mon, 11 Jan 2021 10:29:28 +0000 Message-ID: References: <20210110162008.GV3579531@ZenIV.linux.org.uk> In-Reply-To: <20210110162008.GV3579531@ZenIV.linux.org.uk> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Al Viro On Behalf Of Al Viro > Sent: 10 January 2021 16:20 > > On Thu, Jan 07, 2021 at 08:15:41AM -0500, Mikulas Patocka wrote: > > Hi > > > > I announce a new version of NVFS - a filesystem for persistent memory. > > http://people.redhat.com/~mpatocka/nvfs/ > Utilities, AFAICS > > > git://leontynka.twibright.com/nvfs.git > Seems to hang on git pull at the moment... Do you have it anywhere else? > > > I found out that on NVFS, reading a file with the read method has 10% > > better performance than the read_iter method. The benchmark just reads the > > same 4k page over and over again - and the cost of creating and parsing > > the kiocb and iov_iter structures is just that high. > > Apples and oranges... What happens if you take > > ssize_t read_iter_locked(struct file *file, struct iov_iter *to, loff_t *ppos) > { > struct inode *inode = file_inode(file); > struct nvfs_memory_inode *nmi = i_to_nmi(inode); > struct nvfs_superblock *nvs = inode->i_sb->s_fs_info; > ssize_t total = 0; > loff_t pos = *ppos; > int r; > int shift = nvs->log2_page_size; > size_t i_size; > > i_size = inode->i_size; > if (pos >= i_size) > return 0; > iov_iter_truncate(to, i_size - pos); > > while (iov_iter_count(to)) { > void *blk, *ptr; > size_t page_mask = (1UL << shift) - 1; > unsigned page_offset = pos & page_mask; > unsigned prealloc = (iov_iter_count(to) + page_mask) >> shift; > unsigned size; > > blk = nvfs_bmap(nmi, pos >> shift, &prealloc, NULL, NULL, NULL); > if (unlikely(IS_ERR(blk))) { > r = PTR_ERR(blk); > goto ret_r; > } > size = ((size_t)prealloc << shift) - page_offset; > ptr = blk + page_offset; > if (unlikely(!blk)) { > size = min(size, (unsigned)PAGE_SIZE); > ptr = empty_zero_page; > } > size = copy_to_iter(to, ptr, size); > if (unlikely(!size)) { > r = -EFAULT; > goto ret_r; > } > > pos += size; > total += size; > } while (iov_iter_count(to)); That isn't the best formed loop! David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)