From: Jonathan Nieder <jrnieder@gmail.com>
To: Elijah Newren <newren@gmail.com>
Cc: Jeff King <peff@peff.net>, Git Mailing List <git@vger.kernel.org>,
Jonathan Tan <jonathantanmy@google.com>
Subject: Re: [PATCH] gc: do not warn about too many loose objects
Date: Mon, 16 Jul 2018 14:31:04 -0700 [thread overview]
Message-ID: <20180716213104.GG11513@aiede.svl.corp.google.com> (raw)
In-Reply-To: <CABPp-BEpCF9FE7eJwZWjY+bMsjDQnnDaSrHO+e3DtDDsR-=7Hg@mail.gmail.com>
Elijah Newren wrote:
> I totally agree with your general plan to put unreferenced loose
> objects into a pack. However, I don't think these objects should be
> part of that pack; they should just be deleted instead.
This might be the wrong thread to discuss it, but did you follow the
reference/prune race that Peff mentioned? The simplest cure I'm aware
of to it does involve writing those objects to a pack. The idea is to
enforce a straightforward contract:
There are two kinds of packs: GC and UNREACHABLE_GARBAGE.
Every object in a GC pack has a minimum lifetime of <ttl> (let's say
"1 days") from the time they are read. If you start making use of an
object from a GC pack (e.g. by creating a new object referencing it),
you have three days to ensure it's referenced.
Each UNREACHABLE_GARBAGE pack has a <ttl> (let's say "3 days") from
the time it is created. Objects in an UNREACHABLE_GARBAGE have no
minimum ttl from the time they are read. If you want to start making
use of an object from an UNREACHABLE_GARBAGE pack (e.g. by creating a
new object referencing it), then copy it and everything it references
to a GC pack.
To avoid a proliferation of UNREACHABLE_GARBAGE packs, there's a rule
for coalescing them, but that's not relevant here.
It is perfectly possible for an object in a GC pack to reference an
object in an UNREACHABLE_GARBAGE pack via writes racing with gc, but
that's fine --- on the next gc run, the unreachable garbage objects
get copied to a GC pack.
We've been using this on a JGit DfsRepository based server for > 2
years now and it's been working well. More details are in the "Loose
objects and unreachable objects" section in Documentation/technical/
mentioned before.
Thanks,
Jonathan
next prev parent reply other threads:[~2018-07-16 21:31 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-16 17:27 [PATCH] gc: do not warn about too many loose objects Jonathan Tan
2018-07-16 17:51 ` Jeff King
2018-07-16 18:22 ` Jonathan Nieder
2018-07-16 18:52 ` Jeff King
2018-07-16 19:09 ` Jonathan Nieder
2018-07-16 19:41 ` Jeff King
2018-07-16 19:54 ` Jonathan Nieder
2018-07-16 20:29 ` Jeff King
2018-07-16 20:37 ` Jonathan Nieder
2018-07-16 21:09 ` Jeff King
2018-07-16 21:40 ` Jonathan Nieder
2018-07-16 21:45 ` Jeff King
2018-07-16 22:03 ` Jonathan Nieder
2018-07-16 22:43 ` Jeff King
2018-07-16 22:56 ` Jonathan Nieder
2018-07-16 23:26 ` Jeff King
2018-07-17 1:53 ` Jonathan Nieder
2018-07-17 8:59 ` Ævar Arnfjörð Bjarmason
2018-07-17 14:03 ` Jonathan Nieder
2018-07-17 15:24 ` Ævar Arnfjörð Bjarmason
2018-07-17 20:27 ` Jeff King
2018-07-18 13:11 ` Ævar Arnfjörð Bjarmason
2018-07-18 17:29 ` Jeff King
2018-07-17 15:59 ` Duy Nguyen
2018-07-17 18:09 ` Junio C Hamano
2018-07-16 19:15 ` Elijah Newren
2018-07-16 19:19 ` Jonathan Nieder
2018-07-16 20:21 ` Elijah Newren
2018-07-16 20:35 ` Jeff King
2018-07-16 20:56 ` Jonathan Nieder
2018-07-16 21:12 ` Jeff King
2018-07-16 19:52 ` Jeff King
2018-07-16 20:16 ` Elijah Newren
2018-07-16 20:38 ` Jeff King
2018-07-16 21:09 ` Elijah Newren
2018-07-16 21:21 ` Jeff King
2018-07-16 22:07 ` Elijah Newren
2018-07-16 22:55 ` Jeff King
2018-07-16 23:06 ` Elijah Newren
2018-07-16 21:31 ` Jonathan Nieder [this message]
2018-07-17 6:51 ` [PATCH v2 0/3] gc --auto: do not return error for prior errors in daemonized mode Jonathan Nieder
2018-07-17 6:53 ` [PATCH 1/3] gc: improve handling of errors reading gc.log Jonathan Nieder
2018-07-17 18:19 ` Junio C Hamano
2018-07-17 19:58 ` Jeff King
2018-07-17 6:54 ` [PATCH 2/3] gc: exit with status 128 on failure Jonathan Nieder
2018-07-17 18:22 ` Junio C Hamano
2018-07-17 19:59 ` Jeff King
2018-09-17 18:33 ` Jeff King
2018-09-17 18:40 ` Jonathan Nieder
2018-09-18 17:30 ` Jeff King
2018-07-17 6:57 ` [PATCH 3/3] gc: do not return error for prior errors in daemonized mode Jonathan Nieder
2018-07-17 20:13 ` Jeff King
2018-07-18 16:21 ` Junio C Hamano
2018-07-18 17:22 ` Jeff King
2018-07-18 18:19 ` Junio C Hamano
2018-07-18 19:06 ` Jeff King
2018-07-18 19:55 ` Junio C Hamano
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180716213104.GG11513@aiede.svl.corp.google.com \
--to=jrnieder@gmail.com \
--cc=git@vger.kernel.org \
--cc=jonathantanmy@google.com \
--cc=newren@gmail.com \
--cc=peff@peff.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).