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=-2.8 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 ECEF42023D for ; Thu, 2 Mar 2017 06:12:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750915AbdCBGMl (ORCPT ); Thu, 2 Mar 2017 01:12:41 -0500 Received: from mail-ot0-f173.google.com ([74.125.82.173]:35857 "EHLO mail-ot0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751114AbdCBGMk (ORCPT ); Thu, 2 Mar 2017 01:12:40 -0500 Received: by mail-ot0-f173.google.com with SMTP id i1so45677279ota.3 for ; Wed, 01 Mar 2017 22:10:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=FwT4gqNH26Z22fcQ6QPc5aTun5lTnF9JdXa+6fKDbEM=; b=VuEKhj9K0Oe9TRrHn9uspksT7RZWYuIfMsKyNaHQZlse1lxC13lWRaYj2JOo4VCaV+ GuvrSHNjTeFtRK/5zwvDARNnOHyRiwBQTMslTeULz6bay3CP9kkdtTVcuXo6FGujdom/ MzZwKvd8+kDAPQzKU3sEJ/ergcSTu1xb053J4pP6FtdMJ8JWCxAieahbjPFAnb+4Twrd kjRcEGIzq6B/50d6ksPgfjuxdsEfPC91I2XCWBsHQSIp9m/hBjtyVWQd+DLG0qEuMZMb 3JiVMQlwBZE7MUmvt4EOH3/WOXm++9HH012NfX2FaloZFNIZWKxB1XNaBVs85RXNjHJi Mf6Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=FwT4gqNH26Z22fcQ6QPc5aTun5lTnF9JdXa+6fKDbEM=; b=cFNz1aEduPeN7Kfm2UA7NNY9ym1ou8vzo6el/PiT1c6b/UaxIBbJqpVWoqI2ClcVOh R0t96rXUTepkJ65DY8l4PbObEMKK7llJdGhKMc5a0elorJ+x7Z2S2GD0dAJuBN4cPdY1 b8InFEPbVMieDa6p5DCFB3BRQXo5ybfIZSfmsY3slAMBdVvmyoEut1e1b7Oo/OFBKZRw W1iogQ7Nwxv9oKHZymJQQ5Z1BX2kYIpnQUkyx4ktcKLVARYEWA5rkgqUmXtqENje5pit Nh1yQUMVRLgmrmZOFiIUIxYNB16lnfcOQzFJV1vVwlLwVIDpmqaUmpV0iQhsdyVJ+GH1 c0Bw== X-Gm-Message-State: AMke39k36ucGJc9unmoupZWGMnKeOiihC+hWpYJ43B78iNspcfjlwEgNpSaWQnvtHmYFEcyJ2F48/dWh+0OLVQ== X-Received: by 10.157.20.151 with SMTP id d23mr2601733ote.37.1488435054578; Wed, 01 Mar 2017 22:10:54 -0800 (PST) MIME-Version: 1.0 Received: by 10.74.158.84 with HTTP; Wed, 1 Mar 2017 22:10:23 -0800 (PST) In-Reply-To: <20170301231921.2puf7o7jkrujscwn@sigill.intra.peff.net> References: <20170301231921.2puf7o7jkrujscwn@sigill.intra.peff.net> From: Duy Nguyen Date: Thu, 2 Mar 2017 13:10:23 +0700 Message-ID: Subject: Re: [PATCH] Put sha1dc on a diet To: Jeff King Cc: Linus Torvalds , Johannes Schindelin , Junio C Hamano , Marc Stevens , Dan Shumow , Git Mailing List Content-Type: text/plain; charset=UTF-8 Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Thu, Mar 2, 2017 at 6:19 AM, Jeff King wrote: > You have to remember that some of the Git for Windows users are doing > horrific things like using repositories with 450MB .git/index files, and > the speed to compute the sha1 during an update is noticeable there. We probably should separate this use case from the object hashing anyway. Here we need a better, more reliable crc32 basically, to detect bit flips. Even if we move to SHA-something, we can keep staying with SHA-1 here (and with the fastest implementation) -- Duy