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=-5.2 required=3.0 tests=FROM_EXCESS_BASE64, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 B48B7C3A5A2 for ; Fri, 23 Aug 2019 09:24:59 +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 86CA421726 for ; Fri, 23 Aug 2019 09:24:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 86CA421726 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]:53224 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i15oY-00051P-BA for qemu-devel@archiver.kernel.org; Fri, 23 Aug 2019 05:24:58 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:51680) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i15nY-0004LD-Pe for qemu-devel@nongnu.org; Fri, 23 Aug 2019 05:23:58 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i15nW-0001pR-OQ for qemu-devel@nongnu.org; Fri, 23 Aug 2019 05:23:56 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53866) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i15nW-0001nF-G2 for qemu-devel@nongnu.org; Fri, 23 Aug 2019 05:23:54 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 1C7171801584; Fri, 23 Aug 2019 09:23:53 +0000 (UTC) Received: from redhat.com (ovpn-112-60.ams2.redhat.com [10.36.112.60]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5B6F45C226; Fri, 23 Aug 2019 09:23:51 +0000 (UTC) Date: Fri, 23 Aug 2019 10:23:47 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Markus Armbruster Message-ID: <20190823092347.GA9654@redhat.com> References: <20190822011620.106337-1-aik@ozlabs.ru> <87wof5b7ze.fsf@dusky.pond.sub.org> <20190822144940.GV3267@redhat.com> <87blwg77o4.fsf@dusky.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <87blwg77o4.fsf@dusky.pond.sub.org> User-Agent: Mutt/1.12.0 (2019-05-25) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.63]); Fri, 23 Aug 2019 09:23:53 +0000 (UTC) Content-Transfer-Encoding: quoted-printable 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Alexey Kardashevskiy , Paolo Bonzini , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, Aug 23, 2019 at 07:49:31AM +0200, Markus Armbruster wrote: > Daniel P. Berrang=C3=A9 writes: >=20 > > 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 debuggin= g > >> > as this is way faster than saving the entire RAM to a file and che= cking > >> > 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 varyin= g > > 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. >=20 > Good points. >=20 > The doc strings should spell out "for debugging", like the commit > message does, and both should spell out "weak collision resistance". >=20 > 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-gener= ic/zlib-crc32-1.html >=20 > Care to compare its speed to MD5? I hacked the code to use zlib's crc32 impl and got these for comparison: /crypto/hash/crc32/speed-512: 1089.18 MB/sec OK /crypto/hash/crc32/speed-1024: 1124.63 MB/sec OK /crypto/hash/crc32/speed-4096: 1162.73 MB/sec OK /crypto/hash/crc32/speed-16384: 1171.58 MB/sec OK /crypto/hash/crc32/speed-1048576: 1165.68 MB/sec OK /crypto/hash/md5/speed-512: 476.27 MB/sec OK /crypto/hash/md5/speed-1024: 517.16 MB/sec OK /crypto/hash/md5/speed-4096: 554.70 MB/sec OK /crypto/hash/md5/speed-16384: 564.44 MB/sec OK /crypto/hash/md5/speed-1048576: 566.78 MB/sec OK Regards, Daniel --=20 |: https://berrange.com -o- https://www.flickr.com/photos/dberran= ge :| |: https://libvirt.org -o- https://fstop138.berrange.c= om :| |: https://entangle-photo.org -o- https://www.instagram.com/dberran= ge :|