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=-3.6 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI 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 31A181F404 for ; Mon, 16 Apr 2018 20:19:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751150AbeDPUTI convert rfc822-to-8bit (ORCPT ); Mon, 16 Apr 2018 16:19:08 -0400 Received: from dd28836.kasserver.com ([85.13.147.76]:49409 "EHLO dd28836.kasserver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750799AbeDPUTI (ORCPT ); Mon, 16 Apr 2018 16:19:08 -0400 X-Greylist: delayed 555 seconds by postgrey-1.27 at vger.kernel.org; Mon, 16 Apr 2018 16:19:07 EDT Received: from [192.168.42.152] (dslb-178-000-100-134.178.000.pools.vodafone-ip.de [178.0.100.134]) by dd28836.kasserver.com (Postfix) with ESMTPSA id AF5D53002BB; Mon, 16 Apr 2018 22:09:51 +0200 (CEST) To: larsxschneider@gmail.com (Lars Schneider) Cc: git@vger.kernel.org (Git Mailing List) In-Reply-To: Subject: Re: Optimizing writes to unchanged files during merges? From: lists@haller-berlin.de (Stefan Haller) Date: Mon, 16 Apr 2018 22:09:54 +0200 Message-ID: <1nnder4.l460na1kohjpiM%lists@haller-berlin.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT User-Agent: MacSOUP/2.8.6b1 (Mac OS 10.12.6) Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Lars Schneider wrote: > An engineer works on a task branch and runs incremental builds — all > is good. The engineer switches to another branch to review another > engineer's work. This other branch changes a low-level header file, > but no rebuild is triggered. The engineer switches back to the previous > task branch. At this point, the incremental build will rebuild > everything, as the compiler thinks that the low-level header file has > been changed (because the mtime is different). If you are using C or C++, look into ccache. We're using it to work around this problem, and it's a near-perfect solution, I'd say.