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,URIBL_BLOCKED,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 17217C3A5A1 for ; Thu, 22 Aug 2019 14:53:41 +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 E1D5721848 for ; Thu, 22 Aug 2019 14:53:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E1D5721848 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]:44102 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i0oT6-00072D-1m for qemu-devel@archiver.kernel.org; Thu, 22 Aug 2019 10:53:40 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:36874) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i0oPJ-0003AD-Tv for qemu-devel@nongnu.org; Thu, 22 Aug 2019 10:49:47 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i0oPI-00068g-HT for qemu-devel@nongnu.org; Thu, 22 Aug 2019 10:49:45 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35128) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i0oPI-00068E-92 for qemu-devel@nongnu.org; Thu, 22 Aug 2019 10:49:44 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 88FA918C4269; Thu, 22 Aug 2019 14:49:43 +0000 (UTC) Received: from redhat.com (unknown [10.42.16.132]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B3FDB5D6A7; Thu, 22 Aug 2019 14:49:42 +0000 (UTC) Date: Thu, 22 Aug 2019 15:49:40 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Markus Armbruster Message-ID: <20190822144940.GV3267@redhat.com> References: <20190822011620.106337-1-aik@ozlabs.ru> <87wof5b7ze.fsf@dusky.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <87wof5b7ze.fsf@dusky.pond.sub.org> User-Agent: Mutt/1.12.0 (2019-05-25) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.62]); Thu, 22 Aug 2019 14:49:43 +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: , 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 Thu, Aug 22, 2019 at 04:16:53PM +0200, Markus Armbruster wrote: > Alexey Kardashevskiy writes: > > > 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 > > Any particular reason for MD5? Have you measured the other choices > offered by GLib? > > 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. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|