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,URIBL_BLOCKED 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 6EBCDC3A5A2 for ; Fri, 23 Aug 2019 05:50:50 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3B57B21019 for ; Fri, 23 Aug 2019 05:50:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3B57B21019 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:51802 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i12TJ-0002GH-DI for qemu-devel@archiver.kernel.org; Fri, 23 Aug 2019 01:50:49 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:49499) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i12S9-0000yM-Tm for qemu-devel@nongnu.org; Fri, 23 Aug 2019 01:49:39 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i12S7-0006lX-5N for qemu-devel@nongnu.org; Fri, 23 Aug 2019 01:49:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35750) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i12S6-0006lF-UO for qemu-devel@nongnu.org; Fri, 23 Aug 2019 01:49:35 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C962610F23E0; Fri, 23 Aug 2019 05:49:33 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-117-142.ams2.redhat.com [10.36.117.142]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6F0231001DC0; Fri, 23 Aug 2019 05:49:33 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id E73CF1162B63; Fri, 23 Aug 2019 07:49:31 +0200 (CEST) From: Markus Armbruster To: Daniel P. =?utf-8?Q?Berrang=C3=A9?= References: <20190822011620.106337-1-aik@ozlabs.ru> <87wof5b7ze.fsf@dusky.pond.sub.org> <20190822144940.GV3267@redhat.com> Date: Fri, 23 Aug 2019 07:49:31 +0200 In-Reply-To: <20190822144940.GV3267@redhat.com> ("Daniel P. =?utf-8?Q?Berr?= =?utf-8?Q?ang=C3=A9=22's?= message of "Thu, 22 Aug 2019 15:49:40 +0100") Message-ID: <87blwg77o4.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.66]); Fri, 23 Aug 2019 05:49:33 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [RFC PATCH qemu] qapi: Add query-memory-checksum X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alexey Kardashevskiy , Paolo Bonzini , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Daniel P. Berrang=C3=A9 writes: > On Thu, Aug 22, 2019 at 04:16:53PM +0200, Markus Armbruster wrote: >> Alexey Kardashevskiy writes: >>=20 >> > This returns MD5 checksum of all RAM blocks for migration debugging >> > as this is way faster than saving the entire RAM to a file and checking >> > that. >> > >> > Signed-off-by: Alexey Kardashevskiy >>=20 >> Any particular reason for MD5? Have you measured the other choices >> offered by GLib? >>=20 >> I understand you don't need crypto-strength here. Both MD5 and SHA-1 >> would be bad choices then. > > We have a tests/bench-crypto-hash test but its hardcoded for sha256. > I hacked it to report all algorithms and got these results for varying > input chunk sizes: > > /crypto/hash/md5/speed-512: 519.12 MB/sec OK > /crypto/hash/md5/speed-1024: 560.39 MB/sec OK > /crypto/hash/md5/speed-4096: 591.39 MB/sec OK > /crypto/hash/md5/speed-16384: 576.46 MB/sec OK > /crypto/hash/sha1/speed-512: 443.12 MB/sec OK > /crypto/hash/sha1/speed-1024: 518.82 MB/sec OK > /crypto/hash/sha1/speed-4096: 555.60 MB/sec OK > /crypto/hash/sha1/speed-16384: 568.16 MB/sec OK > /crypto/hash/sha224/speed-512: 221.90 MB/sec OK > /crypto/hash/sha224/speed-1024: 239.79 MB/sec OK > /crypto/hash/sha224/speed-4096: 269.37 MB/sec OK > /crypto/hash/sha224/speed-16384: 274.87 MB/sec OK > /crypto/hash/sha256/speed-512: 222.75 MB/sec OK > /crypto/hash/sha256/speed-1024: 253.25 MB/sec OK > /crypto/hash/sha256/speed-4096: 272.80 MB/sec OK > /crypto/hash/sha256/speed-16384: 275.59 MB/sec OK > /crypto/hash/sha384/speed-512: 322.73 MB/sec OK > /crypto/hash/sha384/speed-1024: 369.84 MB/sec OK > /crypto/hash/sha384/speed-4096: 406.71 MB/sec OK > /crypto/hash/sha384/speed-16384: 417.87 MB/sec OK > /crypto/hash/sha512/speed-512: 320.62 MB/sec OK > /crypto/hash/sha512/speed-1024: 361.93 MB/sec OK > /crypto/hash/sha512/speed-4096: 404.91 MB/sec OK > /crypto/hash/sha512/speed-16384: 418.53 MB/sec OK > /crypto/hash/ripemd160/speed-512: 226.45 MB/sec OK > /crypto/hash/ripemd160/speed-1024: 239.25 MB/sec OK > /crypto/hash/ripemd160/speed-4096: 251.31 MB/sec OK > /crypto/hash/ripemd160/speed-16384: 255.01 MB/sec OK > > > IOW, md5 is clearly the quickest, by a considerable margin over > SHA256/512. SHA1 is slightly slower. > > Assuming that we document that this command is intentionally > *not* trying to guarantee collision resistances we're ok. > > In fact we should not document what kind of checksum is > reported by query-memory-checksum. The impl should be a black > box from user's POV. > > If we're just aiming for debugging tool to detect accidental > corruption, could we even just ignore cryptographic hashs > entirely and do a crc32 - that'd be way faster than even > md5. Good points. The doc strings should spell out "for debugging", like the commit message does, and both should spell out "weak collision resistance". I can't find CRC-32 in GLib, but zlib appears to provide it: http://refspecs.linuxbase.org/LSB_3.0.0/LSB-Core-generic/LSB-Core-generic/z= lib-crc32-1.html Care to compare its speed to MD5?