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, HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_HI,T_DKIM_INVALID, T_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 9D7221F404 for ; Fri, 16 Mar 2018 20:59:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751445AbeCPU7G (ORCPT ); Fri, 16 Mar 2018 16:59:06 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:40754 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751269AbeCPU7F (ORCPT ); Fri, 16 Mar 2018 16:59:05 -0400 Received: by mail-wm0-f67.google.com with SMTP id t6so5387240wmt.5 for ; Fri, 16 Mar 2018 13:59:04 -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:content-transfer-encoding; bh=pN8FqdBAZfVGgcrwC/zbCGUhmynAzeGhJT7Qo4HC6Ts=; b=iF05nbi9uMNxmHyzePWZ3PPa+SQO2x0x4DadenopVm+xAP0g0FaVul0zhtCipWOBKI YrEp0hGb8ulFemK7V2TnlVHr2URA475IPDKwFYl7uIhUllP8bgzrDdtzsWg7VN/yJQML KeaoJLD9VSFZjHRF7hGNX5Gw1MmcmU7Frd7xefCdroCwdCQjd+SEBpmtrZWHTZ3Skt0o PGZkCU8Xqszth23niy9NRjr5Zo6d7bfEQgLwrLSGSZAYmtYj/T3heHNQPDr4CUvQ/n00 LUjXgJ/mk1nIqDogeRKY/wrFNy1JAK5VMN3ndhbLhpL4bdzJDBdL/zohSdl25PvKmHBi rt5A== 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 :content-transfer-encoding; bh=pN8FqdBAZfVGgcrwC/zbCGUhmynAzeGhJT7Qo4HC6Ts=; b=P0QTWBmLv269B4Pci5kzY4rqDrrLds6iy1IOfuqjVuj4CkUi7IvIXD6i3NRCLnqDVM pOxahBWTACpU0ec32Ev9u49PUAg7WG2q/wuJiCjfhxUqFAhxi0gbUzNV91ktwsaazP42 7cxi0NYySxpf1gi5vjHQhBJ9DuZpl8VkuIHSc47DxV8bV1WCSEXCvJOk/PpdC4/Eozg9 yfl6rYjRy7cGQvmQiwMxEd48A7nomHaEW52nryCIzdtwKQ6Z1nBjozqA5CDNhhKJtG5j CU8ZJu2bbS87SgZvA5oy8yJyXC4OL7iVZ6B8mhm6zoLJHGwSk/iQrV3Op5V61Qg72oa5 TQcw== X-Gm-Message-State: AElRT7G9/UHtJU4fp4o9hzsciqskwl3V8KCJMGuqhS3KZ10xAdsBTob6 +4zv0jZX2F9FH4QmcAH4rbnZUlFx X-Google-Smtp-Source: AG47ELuftmuXDRTkOZvCUFjM70aWgu4etgzkACksh0yrjeOMQosUIBBI/1D84BgLhYDzjct3b9cbVg== X-Received: by 10.28.6.205 with SMTP id 196mr3095488wmg.136.1521233943938; Fri, 16 Mar 2018 13:59:03 -0700 (PDT) Received: from localhost (168.50.187.35.bc.googleusercontent.com. [35.187.50.168]) by smtp.gmail.com with ESMTPSA id g25sm8191311wmc.0.2018.03.16.13.59.03 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 16 Mar 2018 13:59:03 -0700 (PDT) From: Junio C Hamano To: =?utf-8?B?Tmd1eeG7hW4gVGjDoWkgTmfhu41j?= Duy Cc: avarab@gmail.com, e@80x24.org, git@vger.kernel.org, peff@peff.net Subject: Re: [PATCH v4 07/11] pack-objects: refer to delta objects by index instead of pointer References: <20180308114232.10508-1-pclouds@gmail.com> <20180316183200.31014-1-pclouds@gmail.com> <20180316183200.31014-8-pclouds@gmail.com> Date: Fri, 16 Mar 2018 13:59:02 -0700 In-Reply-To: <20180316183200.31014-8-pclouds@gmail.com> (=?utf-8?B?Ik5n?= =?utf-8?B?dXnhu4VuIFRow6FpIE5n4buNYw==?= Duy"'s message of "Fri, 16 Mar 2018 19:31:56 +0100") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.2.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Nguyễn Thái Ngọc Duy writes: > These delta pointers always point to elements in the objects[] array > in packing_data struct. We can only hold maximum 4GB of those objects 4GB, as in "number of bytes"? Or "We can hold 4 billion or so of those objects"? > because the array length, nr_objects, is uint32_t. We could use > uint32_t indexes to address these elements instead of pointers. On > 64-bit architecture (8 bytes per pointer) this would save 4 bytes per > pointer. > > Convert these delta pointers to indexes. Since we need to handle NULL > pointers as well, the index is shifted by one [1]. > > [1] This means we can only index 2^32-2 objects even though nr_objects > could contain 2^32-1 objects. It should not be a problem in > practice because when we grow objects[], nr_alloc would probably > blow up long before nr_objects hits the wall.