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=-3.4 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI, T_DKIM_INVALID shortcircuit=no autolearn=ham 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 5FCF31F404 for ; Thu, 12 Apr 2018 21:46:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753378AbeDLVqO (ORCPT ); Thu, 12 Apr 2018 17:46:14 -0400 Received: from mail-wr0-f174.google.com ([209.85.128.174]:33361 "EHLO mail-wr0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752463AbeDLVqN (ORCPT ); Thu, 12 Apr 2018 17:46:13 -0400 Received: by mail-wr0-f174.google.com with SMTP id z73so6473190wrb.0 for ; Thu, 12 Apr 2018 14:46:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:from:to:cc:subject:references:date:in-reply-to:message-id :user-agent:mime-version; bh=oaLNjNyIVjqiRFf/VN4tBviI2UFoWxc+EnR4ywaCLUY=; b=VCLX9dSQw12dWBDPRMMeUuESKKTmdDdid4VNdpGsghkeFLR7VkHcOSdi2eSY4Gxtdl CevBRPKHcpebnRwKb0MYq7y4WOWRu2kVt5nFPu8/nRIqgdVe4LPRZa1JyF8XbROPl13H hA070lMKjrWSsOH/xQtIHbWYnOIc1oFIxK3pdULn86XTL9CTEiClRr2BIdosYZlXRtIK cRQEdTFJGjIdFCvqUzdJ1Ak3WlW3Mst2jnTn9F6WQSRxnruRW9711ZyjUxvEPK/Zn6PS MvV2W7bLmknrORuL5g+/ZpQaekhICaI4eULZxfVr0SO8Vw7BxGYlS6LnGR7M/pPw9Iml JGxg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:from:to:cc:subject:references:date :in-reply-to:message-id:user-agent:mime-version; bh=oaLNjNyIVjqiRFf/VN4tBviI2UFoWxc+EnR4ywaCLUY=; b=r/1gbLD4Fkjw7HlhlViaSbZyQ9U9gkyJJ2ZPD7gExOaop+j/HO1mQhpALe/moCGiDq whWxayr8kq4hjsdIlAuO7QN+ybMfJjxk1NBnkdPDMUv4FbtM8VvjZVfYl7TKZjG04/Wh mvju6LaxxSLimscyr7W2eLbubFd7/fhMFRn482azC59laAOUKjOKtmmxwngZGfcIk+PO IGqalSA81mgERW/t02MZZBGcUYTPiIVLXtJTFPfTBmtSojPO47DyySyTBynIIcRXLKE3 onmtdXaLxCp1PPk7mAoN/56lO8GwA/xUjqVdb5kkWwEyIyTm9Miz3Sywcs1JhG3nNJHT Jscg== X-Gm-Message-State: ALQs6tB9j5oewGX6jzqwZtJsidGjlw2+SCNEWqVBHx/wNR0jVGOXSsA8 Tb4ehie1ttmx8DLkLFqbWaQ= X-Google-Smtp-Source: AIpwx4+PgOrWZVc28lDwOu/g+U4belGoOvKw86JdszkzGuY89XrmWg86Qaqpcc+l0dgUlSomcsjXRw== X-Received: by 10.223.224.141 with SMTP id c13mr2017380wri.88.1523569571875; Thu, 12 Apr 2018 14:46:11 -0700 (PDT) Received: from localhost (112.68.155.104.bc.googleusercontent.com. [104.155.68.112]) by smtp.gmail.com with ESMTPSA id e13sm8492184wrg.79.2018.04.12.14.46.09 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 12 Apr 2018 14:46:10 -0700 (PDT) From: Junio C Hamano To: Linus Torvalds Cc: Git Mailing List Subject: Re: Optimizing writes to unchanged files during merges? References: Date: Fri, 13 Apr 2018 06:46:09 +0900 In-Reply-To: (Linus Torvalds's message of "Thu, 12 Apr 2018 14:14:24 -0700") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.2.50 (gnu/linux) 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 Linus Torvalds writes: > Now, the reason it was marked as changed is that the xfs branch _had_ > in fact changed it, but the changes were already upstream and got > merged away. But the file still got written out (with the same > contents it had before the merge), and 'make' obviously only looks at > modification time, so make rebuilt everything. Thanks for a clear description of the issue. It does sound interesting.