All of lore.kernel.org
 help / color / mirror / Atom feed
From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: "Ted Ts'o" <tytso@mit.edu>, "Jakub Narebski" <jnareb@gmail.com>,
	"Jonathan Nieder" <jrnieder@gmail.com>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"Clemens Buchacher" <drizzd@aon.at>,
	git@vger.kernel.org
Subject: Re: generation numbers
Date: Wed, 06 Jul 2011 16:22:23 -0700	[thread overview]
Message-ID: <7viprfhu4w.fsf@alter.siamese.dyndns.org> (raw)
In-Reply-To: <20110706181200.GD17978@sigill.intra.peff.net> (Jeff King's message of "Wed, 6 Jul 2011 14:12:00 -0400")

Jeff King <peff@peff.net> writes:

> Yeah, that would be fine. With a sorted list of binary sha1s and 32-bit
> generation numbers, you're talking about 24 bytes per commit. Or a 6
> megabyte cache for linux-2.6.
>
> You'd probably want to be a little clever with updates. If I have
> calculated the generation number of every commit, and then do "git
> commit; git tag --contains HEAD", you probably don't want to rewrite the
> entire cache. You could probably journal a fixed number of entries in an
> unsorted file (or even in a parallel directory structure to loose
> objects), and then periodically write out the whole sorted list when the
> journal gets too big. Or choose a more clever data structure that can do
> in-place updates.

As to the low level implementation detail I agree everything you said, but
I have been wondering how the generation number should intereact with
grafts and replaces. It certainly would be safest whenever you change
grafts (which should be a rare event anyway).

  parent reply	other threads:[~2011-07-06 23:22 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-06-11 19:04 [PATCH 0/4] Speed up git tag --contains Ævar Arnfjörð Bjarmason
2011-06-11 19:04 ` [PATCH 1/4] tag: speed up --contains calculation Ævar Arnfjörð Bjarmason
2011-06-11 19:04 ` [PATCH 2/4] limit "contains" traversals based on commit timestamp Ævar Arnfjörð Bjarmason
2011-06-11 19:04 ` [PATCH 3/4] default core.clockskew variable to one day Ævar Arnfjörð Bjarmason
2011-06-11 19:04 ` [PATCH 4/4] Why is "git tag --contains" so slow? Ævar Arnfjörð Bjarmason
2011-07-06  6:40 ` [PATCH 0/4] Speed up git tag --contains Jeff King
2011-07-06  6:54   ` Jeff King
2011-07-06 19:06     ` Clemens Buchacher
2011-07-06  6:56   ` Jonathan Nieder
2011-07-06  7:03     ` Jeff King
2011-07-06 14:26       ` generation numbers (was: [PATCH 0/4] Speed up git tag --contains) Jakub Narebski
2011-07-06 15:01         ` Ted Ts'o
2011-07-06 18:12           ` Jeff King
2011-07-06 18:46             ` Jakub Narebski
2011-07-07 18:59               ` Jeff King
2011-07-07 19:34                 ` generation numbers Junio C Hamano
2011-07-07 20:31                   ` Jakub Narebski
2011-07-07 20:52                     ` A Large Angry SCM
2011-07-08  0:29                       ` Junio C Hamano
2011-07-08 22:57                   ` Jeff King
2011-07-06 23:22             ` Junio C Hamano [this message]
2011-07-07 19:08               ` Jeff King
2011-07-07 20:10                 ` Jakub Narebski
2018-01-12 18:56   ` [PATCH 0/4] Speed up git tag --contains csilvers
2018-03-03  5:15     ` Jeff King
2018-03-08 23:05       ` csilvers
2018-03-12 13:45       ` Derrick Stolee
2018-03-12 23:59         ` Jeff King

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

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=7viprfhu4w.fsf@alter.siamese.dyndns.org \
    --to=gitster@pobox.com \
    --cc=avarab@gmail.com \
    --cc=drizzd@aon.at \
    --cc=git@vger.kernel.org \
    --cc=jnareb@gmail.com \
    --cc=jrnieder@gmail.com \
    --cc=peff@peff.net \
    --cc=tytso@mit.edu \
    /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. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.