From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-1.9 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_HI,T_RP_MATCHES_RCVD shortcircuit=no autolearn=no autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 765FC1FA7B for ; Fri, 16 Jun 2017 21:39:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752252AbdFPVjE (ORCPT ); Fri, 16 Jun 2017 17:39:04 -0400 Received: from mail-wm0-f49.google.com ([74.125.82.49]:36134 "EHLO mail-wm0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752087AbdFPVjD (ORCPT ); Fri, 16 Jun 2017 17:39:03 -0400 Received: by mail-wm0-f49.google.com with SMTP id m125so36159736wmm.1 for ; Fri, 16 Jun 2017 14:39:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:references:user-agent:in-reply-to:date :message-id:mime-version; bh=JIL5Y+r40RyqvUN+KbNLb8bK3JOyWDekxgRfk/Tx5Po=; b=jEHtdVEP1tkhvKalIfxhVgl5dSVWsEFZ0XwexLY5pHLQA6b/LEc8MK85iNHYN1SmVq M2sHWQNbI+kFcNJuwVDRz1LuqetITd4dWN2LHuHsh4TEpO31ozDMg0F/u9937vBQdsXt pRNfi21Qzi2O1WJNQa+h1FXCa93ekdeXJtPCT3spOyjENlnMTbaUoesXBXwzkZZKf3Sz /TnIiHt/1MnugKGrlxdIiEYdzgW07U5kzkBgJNgM6SCSJir1qeMm04jwGHPpo+Erj1kl ygYXe0a2ls0Tv7EpzDDPoslbt85yV4PBOS+QQ2r7bEDTDTFJ9HauEOdA973CIvquwQdu V78A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:references:user-agent :in-reply-to:date:message-id:mime-version; bh=JIL5Y+r40RyqvUN+KbNLb8bK3JOyWDekxgRfk/Tx5Po=; b=rCw8f91d/cQ4vWgBQvH3HsA9ABFPOa/tpk2kFQ8XHa/sDWXHkrIEAJJWYbTg0828iY GAl42CxRUdTD7Ezi7Be/RyqrO7B7IaLhs6r75ABtPo4QY6y+rEyXauBLEfMH6HkRlqbQ cAKe9J0+iZF1C0cX/t6royRU8kguY5Umus3mSMf1S+kZIw5bviUsSqidYeeYNXY0LOa6 w1Y76SOsSAciUKgpugwq980Q0QIj7XhmScv9/T2qPKVUlUEpHnGqdBJpWP9TNJ49yfmn ZAIj1CzfCpcGhg+4kF6JQQtGM2fawTV8gxbF9VM/roIIU7FVqCeYqQPkTG9BSAW+NUgy pApg== X-Gm-Message-State: AKS2vOwNmBSNKnlLrVqJLbnvkeHl5AMDgjMEDy0wV8LT/AgD3KrnJTbx ldZb1HgKswe4jA== X-Received: by 10.80.146.47 with SMTP id i44mr8591239eda.48.1497649142083; Fri, 16 Jun 2017 14:39:02 -0700 (PDT) Received: from snth ([92.109.130.42]) by smtp.gmail.com with ESMTPSA id p20sm1932123eda.67.2017.06.16.14.39.00 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 16 Jun 2017 14:39:00 -0700 (PDT) Received: from avar by snth with local (Exim 4.84_2) (envelope-from ) id 1dLyxI-0002UJ-4G; Fri, 16 Jun 2017 23:39:00 +0200 From: =?utf-8?B?w4Z2YXIgQXJuZmrDtnLDsA==?= Bjarmason To: Jonathan Nieder Cc: Junio C Hamano , Adam Langley , Johannes Schindelin , "brian m. carlson" , Jeff King , Mike Hommey , Brandon Williams , Linus Torvalds , Git Mailing List , Stefan Beller , Jonathan Tan Subject: Re: Which hash function to use, was Re: RFC: Another proposed hash function transition plan References: <20170615224110.kvrjs3lmwxcoqfaw@genre.crustytoothpaste.net> <20170616001738.affg4qby7y7yahos@genre.crustytoothpaste.net> <87y3ss8n4h.fsf@gmail.com> <20170616212414.GC133952@aiede.mtv.corp.google.com> User-agent: Debian GNU/Linux 8.8 (jessie); Emacs 25.1.1; mu4e 0.9.19 In-reply-to: <20170616212414.GC133952@aiede.mtv.corp.google.com> Date: Fri, 16 Jun 2017 23:39:00 +0200 Message-ID: <87tw3f8vez.fsf@gmail.com> MIME-Version: 1.0 Content-Type: text/plain Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Fri, Jun 16 2017, Jonathan Nieder jotted: > Part of the reason I suggested previously that it would be helpful to > try to benchmark Git with various hash functions (which didn't go over > well, for some reason) is that it makes these comparisons more > concrete. Without measuring, it is hard to get a sense of the > distribution of input sizes and how much practical effect the > differences we are talking about have. It would be great to have such benchmarks (I probably missed the "didn't go over well" part), but FWIW you can get pretty close to this right now in git by running various t/perf benchmarks with BLKSHA1/OPENSSL/SHA1DC. Between the three of those (particularly SHA1DC being slower than OpenSSL) you get a similar performance difference as some SHA-1 v.s. SHA-256 benchmarks I've seen, so to the extent that we have existing performance tests it's revealing to see what's slower & faster. It makes a particularly big difference for e.g. p3400-rebase.sh.