From: Junio C Hamano <gitster@pobox•com>
To: Duy Nguyen <pclouds@gmail•com>
Cc: Git Mailing List <git@vger•kernel.org>,
Stefan Beller <sbeller@google•com>,
Thomas Rast <tr@thomasrast•ch>
Subject: Re: pack negotiation algorithm between 2 share-nothing repos
Date: Wed, 26 Aug 2015 09:49:56 -0700 [thread overview]
Message-ID: <xmqqbnduuh8r.fsf@gitster.dls.corp.google.com> (raw)
In-Reply-To: <xmqqk2t0mrhi.fsf@gitster.dls.corp.google.com> (Junio C. Hamano's message of "Wed, 12 Aug 2015 08:55:05 -0700")
Junio C Hamano <gitster@pobox•com> writes:
> Duy Nguyen <pclouds@gmail•com> writes:
>
>> I know this is a corner case, but because it has a valid use case,
>> maybe we should do something about it. Immediate reaction is to add an
>> option to send no "have"s. But maybe you guys have better ideas.
>
> This and similar corner cases were discussed in very early days of
> Git.
>
> One interesting idea floated back then but was not pursued was to
> dig and send have's sparsely and then back up. Instead of digging
> and sending _all_ commits in a contiguous history, after sending the
> tip, you skip the commits from the history before sending the next
> one, and progressively make the skipping larger (e.g. Fibonacci, or
> exponential). You need to remember what you sent and for each of
> what you sent its topologically-oldest descendant you sent earlier
> that you heard the other side does not have.
>
> Then, when you get an Ack, you know a stretch of history between a
> commit that is known to be common (i.e. the one you heard an Ack
> just now) and its descendant that is known only to you (i.e. the
> topologically-oldest one you remember that you did send and they
> didn't say is common). At that point, you and the other end can
> bisect that range.
If anybody is interested, here is a good place to start:
http://thread.gmane.org/gmane.comp.version-control.git/96149/focus=102485
[Cc'ed Stefan as I think he was collecting possible enhancement to
put in the protocol v2].
prev parent reply other threads:[~2015-08-26 16:50 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-12 11:27 pack negotiation algorithm between 2 share-nothing repos Duy Nguyen
2015-08-12 15:55 ` Junio C Hamano
2015-08-26 16:49 ` Junio C Hamano [this message]
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