From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-3.6 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI shortcircuit=no autolearn=ham autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 798931F954 for ; Thu, 23 Aug 2018 02:28:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727574AbeHWFzV (ORCPT ); Thu, 23 Aug 2018 01:55:21 -0400 Received: from mail-pg1-f176.google.com ([209.85.215.176]:39763 "EHLO mail-pg1-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727473AbeHWFzV (ORCPT ); Thu, 23 Aug 2018 01:55:21 -0400 Received: by mail-pg1-f176.google.com with SMTP id m3-v6so883938pgp.6 for ; Wed, 22 Aug 2018 19:27:59 -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=zTu25rvHlXj+4uNqtkiakbVvfLFo4HAwBI3q3Om5yYg=; b=WRiXnIGnyQgStPJl6YowjsteykNIAvH/Rl+7rnBfbKC68kJo/9B9+9t0pKartmqBkd PrYaubLwAkWpGad/0/BpXAzMleRFvsdAIZ+06W+IKrdmFtyt4YEQPisAGL4VULYzkch3 HqsiCj61gHUVpRpC/PfAAmOBqjpevcoL95WIAg0x2pDKY4VTtf21511QZVQE7E8vAhg+ hXuzl03JtmRAWzuwlQJAjLmOaRHzHvFusNs13gZGx5X5i5idfJVD112FsTqAarNUGbzA OnMHnoWQyrj6dMeB/S+xl5PvGDWjD5X2AcoFGv2Y/6Kn95brRn1CEk0w6eipiSHevQPA CXTA== 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=zTu25rvHlXj+4uNqtkiakbVvfLFo4HAwBI3q3Om5yYg=; b=WE9Xgh7yX06IidONVzzsTMqDvOKW8dS4hZ2tE9WoOM11StwDUOnLxrlOUaeQFrAKMa m5r16IxX4woi0Jwomxs4QcwQtA808hCWLvaBj/o2pgVxtHPtqz6j/O6fKQMKodXNxo1M G2Wu1cunARjrVMsEBRJMZIMYzMQciflyCqmzgDIlsOv9uXC7RyyITOrFvynAqUzdEJ+P EbGkEg8QonOE8rjX56kNUhTWbdWl0c1a+fNzLkD1blU1bpVE16mobkGZt3sd8OEsmhLq 2Nx3XFcImaQJ1beZg1UdJkC95J5RD3I1MRviLvubYz/aIpSP/hJklL4z7+ifLGuvVEyP 7Igg== X-Gm-Message-State: AOUpUlGeySZpxd510CZtxAkeA/6wmW+UiTmCOirg0PQtTZWYaXPR0VKq XI0OI/qcJG3+1GDoDzVOMU4= X-Google-Smtp-Source: AA+uWPyp64VBKxAh5xODG9/ZeduIpqnQDyLlrrmujBWJJTY59dLyL0qKI8WsXqK9MyLWLFly4VV6ag== X-Received: by 2002:a63:e841:: with SMTP id a1-v6mr27269654pgk.126.1534991278792; Wed, 22 Aug 2018 19:27:58 -0700 (PDT) Received: from aiede.svl.corp.google.com ([2620:0:100e:422:4187:1d6c:d3d6:9ce6]) by smtp.gmail.com with ESMTPSA id i26-v6sm3807632pfo.107.2018.08.22.19.27.58 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 22 Aug 2018 19:27:58 -0700 (PDT) Date: Wed, 22 Aug 2018 19:27:56 -0700 From: Jonathan Nieder To: Jeff King Cc: Paul Smith , git@vger.kernel.org, Derrick Stolee , Duy Nguyen , =?utf-8?B?w4Z2YXIgQXJuZmrDtnLDsA==?= Bjarmason , "brian m. carlson" Subject: Re: [ANNOUNCE] Git v2.19.0-rc0 Message-ID: <20180823022756.GF92374@aiede.svl.corp.google.com> References: <1b20b754-987c-a712-2594-235b845bc5d0@gmail.com> <20180821212923.GB24431@sigill.intra.peff.net> <20180822004815.GA535143@genre.crustytoothpaste.net> <20180822030344.GA14684@sigill.intra.peff.net> <814549a01074e89a4b26cb0cf13e4dddeb3a040a.camel@mad-scientist.net> <20180822152306.GC32630@sigill.intra.peff.net> <20180823012343.GB92374@aiede.svl.corp.google.com> <20180823021618.GA12052@sigill.intra.peff.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180823021618.GA12052@sigill.intra.peff.net> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Jeff King wrote: > FWIW, it's not 10%. The best I measured was ~4% on a very > hashcmp-limited operation, and I suspect even that may be highly > dependent on the compiler. We might be able to improve more by > sprinkling more asserts around, but there are 75 mentions of > the_hash_algo->rawsz. I wouldn't want to an assert at each one. > > I don't mind doing one or a handful of these asserts as part of v2.19 if > we want to try to reclaim those few percent. But I suspect the very > first commit in any further hash-transition work is just going to be to > rip them all out. I was thinking just hashcmp and hashcpy. Ideally such a change would come with a performance test to help the person writing that very first commit. Except we already have performance tests that capture this. ;-) For further hash-transition work, I agree someone may want to revert this, and I don't mind such a revert appearing right away in "next". And it's possible that we might have to do the equivalent of manual template expansion to recover the performance in some performance-sensitive areas. Maybe we can get the compiler to cooperate with us in that and maybe we can't. That's okay with me. Anyway, I'll resend your patch with a commit message added some time this evening. Thanks, Jonathan