From patchwork Tue May 14 18:47:43 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Derrick Stolee X-Patchwork-Id: 10943581 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9450D933 for ; Tue, 14 May 2019 18:48:02 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 84CF428869 for ; Tue, 14 May 2019 18:48:02 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 78B0F28895; Tue, 14 May 2019 18:48:02 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FROM,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8E6D528869 for ; Tue, 14 May 2019 18:48:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727542AbfENSsA (ORCPT ); Tue, 14 May 2019 14:48:00 -0400 Received: from mail-yb1-f196.google.com ([209.85.219.196]:45978 "EHLO mail-yb1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726201AbfENSr7 (ORCPT ); Tue, 14 May 2019 14:47:59 -0400 Received: by mail-yb1-f196.google.com with SMTP id v2so47798ybm.12 for ; Tue, 14 May 2019 11:47:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=kkfZwyd2XPzl1/26kyJQWNg9v3n0OiXSvbErJd17AbQ=; b=r/ZsSucpnKtzOnqFKeVxPWSgdRsOLrdB2RPMcFff/1GZxLKPBi7PC+JieDmc/izHcS s0bS8pTjITCEkjVO+hqejTpjqjOHEl1ctvgyRZS6x3LlC7rjMqxltuir7RQ0edR2IGFd NnejOXVmUaZhMb9vxPApHzuzl+UFEwrrsjeZ/sXKL+UAX7HIcP87g7vSlqOUXKeryZia /mtGucvdgBfsPhjyey6Fc1HYCUJB/y7HEOrCNgQp6W+8vmQ6Hs4i2QGCN+ICneKreD2y 1heUdA3UBLNGWiwtUSfo50gr+/livLwQQSG7FTqMZAczylpMG7f932yHEv32yNcRNOAJ ppuQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=kkfZwyd2XPzl1/26kyJQWNg9v3n0OiXSvbErJd17AbQ=; b=LGbo9Mnzi207uJllQep93O1WnI7+oXGue2Q3UU4pkYw2WvH/IyyGiC4OHnDLw34dHi MfDqxnOZnKDo6oaCv/qG2H1rJ4XaFZpPfpxdXb6kNySVzlQJOX0YOyzWrgFfEIBKjk1w DX1+9PR6um4xmqGYjZ4GssyjqHHNclgjAjxjR/hNLZ6vF1ylqi90yvot1IRQaptp4pGV gbe4y6xZ53pAPUp5q6t2NNW3zmheEP+hMkgN8P4L2X9xOz4BLWxbGy99CRmw7Dl3XdMe F9q0Xm3qg9/ETs3Tr82ILzdbpNAN3J8sUFDwv2xt4jksiya0q8b82PNB8aKJR6i2N9N+ 6zaA== X-Gm-Message-State: APjAAAXyZ+PhRZHxKlA6xpqt6SbFxwT7HTajL+xZXavbGA2eGvw60HO/ etEK3wcJ7m4omjffVAp3SpluD9EIZsM= X-Google-Smtp-Source: APXvYqxI1XaxCHQGzaxur2atYceCwtAS7icmPrk8MukcYBVg9tDW5b1RgVPklqi+FHKdoG69WtcIGw== X-Received: by 2002:a5b:ac9:: with SMTP id a9mr16866536ybr.160.1557859678319; Tue, 14 May 2019 11:47:58 -0700 (PDT) Received: from linux.mshome.net ([98.122.173.75]) by smtp.gmail.com with ESMTPSA id u17sm3438627ywu.94.2019.05.14.11.47.56 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 14 May 2019 11:47:56 -0700 (PDT) From: Derrick Stolee X-Google-Original-From: Derrick Stolee To: git@vger.kernel.org Cc: peff@peff.net, jrnieder@gmail.com, gitster@pobox.com, avarab@gmail.com, dstolee@microsoft.com Subject: [PATCH v6 00/11] Create 'expire' and 'repack' verbs for git-multi-pack-index Date: Tue, 14 May 2019 18:47:43 +0000 Message-Id: <20190514184754.3196-1-dstolee@microsoft.com> X-Mailer: git-send-email 2.22.0.rc0 In-Reply-To: <20190424151428.170316-1-dstolee@microsoft.com> References: <20190424151428.170316-1-dstolee@microsoft.com> MIME-Version: 1.0 Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP The multi-pack-index provides a fast way to find an object among a large list of pack-files. It stores a single pack-reference for each object id, so duplicate objects are ignored. Among a list of pack-files storing the same object, the most-recently modified one is used. Create new subcommands for the multi-pack-index builtin. * 'git multi-pack-index expire': If we have a pack-file indexed by the multi-pack-index, but all objects in that pack are duplicated in more-recently modified packs, then delete that pack (and any others like it). Delete the reference to that pack in the multi-pack-index. * 'git multi-pack-index repack --batch-size=': Starting from the oldest pack-files covered by the multi-pack-index, find those whose "expected size" is below the batch size until we have a collection of packs whose expected sizes add up to the batch size. We compute the expected size by multiplying the number of referenced objects by the pack-size and dividing by the total number of objects in the pack. If the batch-size is zero, then select all packs. Create a new pack containing all objects that the multi-pack-index references to those packs. This allows us to create a new pattern for repacking objects: run 'repack'. After enough time has passed that all Git commands that started before the last 'repack' are finished, run 'expire' again. This approach has some advantages over the existing "repack everything" model: 1. Incremental. We can repack a small batch of objects at a time, instead of repacking all reachable objects. We can also limit ourselves to the objects that do not appear in newer pack-files. 2. Highly Available. By adding a new pack-file (and not deleting the old pack-files) we do not interrupt concurrent Git commands, and do not suffer performance degradation. By expiring only pack-files that have no referenced objects, we know that Git commands that are doing normal object lookups* will not be interrupted. * Note: if someone concurrently runs a Git command that uses get_all_packs(), * then that command could try to read the pack-files and pack-indexes that we * are deleting during an expire command. Such commands are usually related to * object maintenance (i.e. fsck, gc, pack-objects) or are related to * less-often-used features (i.e. fast-import, http-backend, server-info). We **are using** this approach in VFS for Git to do background maintenance of the "shared object cache" which is a Git alternate directory filled with packfiles containing commits and trees. We currently download pack-files on an hourly basis to keep up-to-date with the central server. The cache servers supply packs on an hourly and daily basis, so most of the hourly packs become useless after a new daily pack is downloaded. The 'expire' command would clear out most of those packs, but many will still remain with fewer than 100 objects remaining. The 'repack' command (with a batch size of 1-3gb, probably) can condense the remaining packs in commands that run for 1-3 min at a time. Since the daily packs range from 100-250mb, we will also combine and condense those packs. Updates in V6: I rebased onto ds/midx-too-many-packs. Thanks, Junio for taking that change first. There were several subtle things that needed to change to put this change on top: * We need a repository struct everywhere since we add pack-files to the packed_git list now. * A FREE_AND_NULL() was dropped after closing a pack because the pack is still in the packed_git list after opening. * I noticed some whitespace problems. I also expect GMail to munge my added "From:" tags, so it will look like the author is "stolee@gmail.com" instead of "dstolee@microsoft.com". Sorry for the continued inconvenience here. Thanks, -Stolee Derrick Stolee (11): repack: refactor pack deletion for future use Docs: rearrange subcommands for multi-pack-index multi-pack-index: prepare for 'expire' subcommand midx: simplify computation of pack name lengths midx: refactor permutation logic and pack sorting multi-pack-index: implement 'expire' subcommand multi-pack-index: prepare 'repack' subcommand midx: implement midx_repack() multi-pack-index: test expire while adding packs midx: add test that 'expire' respects .keep files t5319-multi-pack-index.sh: test batch size zero Documentation/git-multi-pack-index.txt | 32 +- builtin/multi-pack-index.c | 14 +- builtin/repack.c | 14 +- midx.c | 440 +++++++++++++++++++------ midx.h | 2 + packfile.c | 28 ++ packfile.h | 7 + t/t5319-multi-pack-index.sh | 184 +++++++++++ 8 files changed, 602 insertions(+), 119 deletions(-)