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=-3.1 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,RCVD_IN_SORBS_SPAM, 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 6413F2095D for ; Wed, 22 Mar 2017 22:02:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751355AbdCVWCw (ORCPT ); Wed, 22 Mar 2017 18:02:52 -0400 Received: from mail-pg0-f44.google.com ([74.125.83.44]:35235 "EHLO mail-pg0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751153AbdCVWCu (ORCPT ); Wed, 22 Mar 2017 18:02:50 -0400 Received: by mail-pg0-f44.google.com with SMTP id t143so47520763pgb.2 for ; Wed, 22 Mar 2017 15:02:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=uvcthn18FZPWGEp2zFPOzDMXTOLFINliQtaAjOD9ghA=; b=qcnT31prxT89BWc/aDRul5rVJiE+l/Ij1th2+cjkYSq4d8Lwg+duWJNVF1Cvqttkk2 +xPoJ0Q22SivhblRGHJSdnDq91IAVHi2jDu3F5DBRsq+jl6+Flw+7rc1R7CbRMDxh+5S kz8W5mTyB6JxSbRz7ByUiXgCmfGYXOu6Zg4J6EOgqqYGPEd2AcKYFO0giQX+WzDzJCg5 ZtUCNKBqBDV9IjmbSFmq3bmOEtvGthiNgBRYcfXbmOp/THP+m9zOhnsNsymsFWisByVd 9Lvh+rGKKtS91tRBRM7qc1SgAdgODU0XKGFnzmgEOl1YvkLUJpipo+mQ8YM9K3SH2gzo j2Ew== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=uvcthn18FZPWGEp2zFPOzDMXTOLFINliQtaAjOD9ghA=; b=lpvQMmzUUPw9CgZpm+XTY4vA49donR5Kh0+SF8KeTk54x/aA5GMPDHk6ldPnPNP0S2 SJGgm6Y8s5giBXWX5eQGpnXkgP0rVTRraohizjQ0XQ6bA48t9KGTW1VvfWmQGpNjcgtG hvT+rC/9sEtkOYPIXAeqWnL/Xq8NQ7hov/H1XNP8fLAdQrsXbdgnwzyoUZLpCydZNiCx R3Fwff6k59ghesXACGx6eEWGsIMa70rlrRkaG8DPh8UjAWNn5/gg046yMrq5Pxj+31zz H6mhi0FHyFZCj5/SonGXFyK6A9kMQ7WAn2rYjbuOU5dppLXETcEnLElXJZTDzB03bYXe c/9A== X-Gm-Message-State: AFeK/H1xeUZR25LozB9dfnA2B+CKZ23m3Lv0epJ0gZfWUib2sTVkwamW9CedoCgXtRO69w== X-Received: by 10.98.16.11 with SMTP id y11mr48147909pfi.84.1490220169506; Wed, 22 Mar 2017 15:02:49 -0700 (PDT) Received: from aiede.mtv.corp.google.com ([2620:0:1000:5b10:55f5:992d:bc78:c749]) by smtp.gmail.com with ESMTPSA id t6sm5825203pgt.8.2017.03.22.15.02.48 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Wed, 22 Mar 2017 15:02:48 -0700 (PDT) Date: Wed, 22 Mar 2017 15:02:46 -0700 From: Jonathan Nieder To: Johannes Schindelin Cc: Junio C Hamano , Lars Schneider , Jeff King , Git Mailing List , Linus Torvalds Subject: Re: USE_SHA1DC is broken in pu Message-ID: <20170322220246.GD26108@aiede.mtv.corp.google.com> References: <2B1DE627-11C8-4FA5-A354-76B6C475666A@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Hi, Johannes Schindelin wrote: > As to the default of seriously slowing down all SHA-1 computations: since > you made that the default, at compile time, with no way to turn on the > faster computation, this will have a major, negative impact. Are you > really, really sure you want to do that? > > I thought that it was obvious that we would have at least a runtime option > to lessen the load. It's not obvious to me. I agree that the DC_SHA1 case can be sped up, e.g. by turning off the collision detection for sha1 calculations that are not part of fetching, receiving a push, or running fsck. To be clear, are you saying that this is a bad compile-time default because distributors are going to leave it and end-users will end up with a bad experience? Or are you saying distributors have no good alternative to choose at compile time? Or something else? Is there some particular downstream that this breaks? Thanks and hope that helps, Jonathan