From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lists.gentoo.org (pigeon.gentoo.org [208.92.234.80]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by finch.gentoo.org (Postfix) with ESMTPS id BA2541396D9 for ; Sat, 21 Oct 2017 08:20:36 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id C9E602BC032; Sat, 21 Oct 2017 08:20:31 +0000 (UTC) Received: from smtp.gentoo.org (woodpecker.gentoo.org [IPv6:2001:470:ea4a:1:5054:ff:fec7:86e4]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by pigeon.gentoo.org (Postfix) with ESMTPS id 777CD2BC009 for ; Sat, 21 Oct 2017 08:20:29 +0000 (UTC) Received: from pomiot (d202-252.icpnet.pl [109.173.202.252]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: mgorny) by smtp.gentoo.org (Postfix) with ESMTPSA id 5E84333BF0B; Sat, 21 Oct 2017 08:20:27 +0000 (UTC) Message-ID: <1508574023.844.2.camel@gentoo.org> Subject: Re: [gentoo-dev] Manifest2 hashes, take n+1-th From: =?UTF-8?Q?Micha=C5=82_G=C3=B3rny?= To: gentoo-dev@lists.gentoo.org Date: Sat, 21 Oct 2017 10:20:23 +0200 In-Reply-To: References: <1508440120.19870.14.camel@gentoo.org> <0077e13e-e525-4e0e-5a43-6b05cefa221a@gentoo.org> <1508516126.1490.9.camel@gentoo.org> Organization: Gentoo Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.24.5 Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-dev@lists.gentoo.org Reply-to: gentoo-dev@lists.gentoo.org Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-Archives-Salt: 551da674-e328-4cb2-a29b-401da7aa1ce3 X-Archives-Hash: c4f4b07ec4161aa161d7669001f67922 W dniu sob, 21.10.2017 o godzinie 10∶01 +0200, użytkownik Paweł Hajdan, Jr. napisał: > On 20/10/2017 18:15, Michał Górny wrote: > > W dniu pią, 20.10.2017 o godzinie 17∶42 +0200, użytkownik Paweł Hajdan, > > Jr. napisał: > > > Curious, do we have any measurements/estimates of the performance cost? > > > > With a single thread serial processing of all hashes, it's just sum of > > times involved in every hash, i.e. Th = T1 + T2 + T3 + ... You'd have to > > get some numbers to get something smarter out of it. > > > > If we assume we can do N threads, then cost of N algorithms is equal to > > the slowest of them all. Which implies that having N algorithms is > > fastest on systems capable of at least N threads. > > > > Taking a random comparison [1], it seems that SHA3/512 is 3-5 times > > slower than SHA2/512. > > How large part of dependency calculation / other portage's operation is > this though? > > My point is, did profiling turn out hash computation as bottleneck, or > is this more speculative? Purely speculative. > I'm still in favor of modernizing the hashes, just somewhat skeptical > when performance is being mentioned. > FWICS BLAKE2 can be even 2.5 times faster than SHA2, so we'll probably go with that. In this case, the performance impact will be negligible -- in fact, it should be faster than the current set of three hashes. -- Best regards, Michał Górny