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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=no 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 E8CBAC33CAF for ; Tue, 14 Jan 2020 00:41:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BEFFD207FD for ; Tue, 14 Jan 2020 00:41:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729186AbgANAl4 (ORCPT ); Mon, 13 Jan 2020 19:41:56 -0500 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:49084 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728641AbgANAlz (ORCPT ); Mon, 13 Jan 2020 19:41:55 -0500 Received: from callcc.thunk.org (guestnat-104-133-0-111.corp.google.com [104.133.0.111] (may be forged)) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 00E0fbEI006931 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 13 Jan 2020 19:41:38 -0500 Received: by callcc.thunk.org (Postfix, from userid 15806) id 5C3A54207DF; Mon, 13 Jan 2020 19:41:37 -0500 (EST) Date: Mon, 13 Jan 2020 19:41:37 -0500 From: "Theodore Y. Ts'o" To: Eric Biggers Cc: linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, Victor Hsieh , linux-f2fs-devel@lists.sourceforge.net Subject: Re: [PATCH v3] fs-verity: implement readahead for FS_IOC_ENABLE_VERITY Message-ID: <20200114004137.GQ76141@mit.edu> References: <20200106205410.136707-1-ebiggers@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200106205410.136707-1-ebiggers@kernel.org> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, Jan 06, 2020 at 12:54:10PM -0800, Eric Biggers wrote: > From: Eric Biggers > > When it builds the first level of the Merkle tree, FS_IOC_ENABLE_VERITY > sequentially reads each page of the file using read_mapping_page(). > This works fine if the file's data is already in pagecache, which should > normally be the case, since this ioctl is normally used immediately > after writing out the file. > > But in any other case this implementation performs very poorly, since > only one page is read at a time. > > Fix this by implementing readahead using the functions from > mm/readahead.c. > > This improves performance in the uncached case by about 20x, as seen in > the following benchmarks done on a 250MB file (on x86_64 with SHA-NI): > > FS_IOC_ENABLE_VERITY uncached (before) 3.299s > FS_IOC_ENABLE_VERITY uncached (after) 0.160s > FS_IOC_ENABLE_VERITY cached 0.147s > sha256sum uncached 0.191s > sha256sum cached 0.145s > > Note: we could instead switch to kernel_read(). But that would mean > we'd no longer be hashing the data directly from the pagecache, which is > a nice optimization of its own. And using kernel_read() would require > allocating another temporary buffer, hashing the data and tree pages > separately, and explicitly zero-padding the last page -- so it wouldn't > really be any simpler than direct pagecache access, at least for now. > > Signed-off-by: Eric Biggers Looks good, feel free to add: Reviewed-by: Theodore Ts'o