From: Jeff King <peff@peff.net>
To: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Cc: Jonathan Tan <jonathantanmy@google.com>,
Brandon Williams <bmwill@google.com>,
git@vger.kernel.org, git@jeffhostetler.com
Subject: Re: [PATCH] oidmap: map with OID as key
Date: Fri, 29 Sep 2017 19:24:13 -0400 [thread overview]
Message-ID: <20170929232412.mmimg7srkjsypg2y@sigill.intra.peff.net> (raw)
In-Reply-To: <alpine.DEB.2.21.1.1709292341280.40514@virtualbox>
On Fri, Sep 29, 2017 at 11:43:57PM +0200, Johannes Schindelin wrote:
> On Thu, 28 Sep 2017, Jeff King wrote:
>
> > If you're planning on using an oidset to mark every object in a
> > 100-million-object monorepo, we'd probably care more. But I'd venture to
> > say that any scheme which involves generating that hash table on the fly
> > is doing it wrong. At at that scale we'd want to look at compact
> > mmap-able on-disk representations.
>
> Or maybe you would look at a *not-so-compact* mmap()able on-disk
> representation, to allow for painless updates.
>
> You really will want to avoid having to write out large files just because
> a small part of them changed. We learn that lesson the hard way, from
> having to write 350MB worth of .git/index for every single, painful `git
> add` operation.
Sure. I didn't mean to start designing the format. I just mean that if
the first step of the process is "read information about all 100 million
objects into an in-RAM hashmap", then that is definitely not going to
fly.
-Peff
next prev parent reply other threads:[~2017-09-29 23:24 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-27 22:19 [PATCH] oidmap: map with OID as key Jonathan Tan
2017-09-28 0:41 ` Brandon Williams
2017-09-28 17:46 ` Jonathan Tan
2017-09-28 20:05 ` Jeff King
2017-09-29 19:04 ` Jonathan Tan
2017-09-29 19:26 ` Jeff King
2017-09-29 21:43 ` Johannes Schindelin
2017-09-29 23:24 ` Jeff King [this message]
2017-09-28 3:13 ` Junio C Hamano
2017-09-28 17:38 ` Jonathan Tan
2017-09-29 22:54 ` [PATCH v2] " Jonathan Tan
2017-10-02 23:48 ` Brandon Williams
2017-10-03 6:31 ` Jeff King
2017-10-04 0:29 ` Jonathan Tan
2017-10-04 7:45 ` Jeff King
2017-10-04 8:48 ` Junio C Hamano
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