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From: Jonathan Tan <jonathantanmy@google.com>
To: peff@peff.net
Cc: jonathantanmy@google.com, git@vger.kernel.org
Subject: Re: Git in Outreachy December 2019?
Date: Mon, 23 Sep 2019 13:38:54 -0700	[thread overview]
Message-ID: <20190923203854.171170-1-jonathantanmy@google.com> (raw)
In-Reply-To: <20190923191509.GC21344@sigill.intra.peff.net>

> I think this is an OK level of detail. I'm not sure quite sure about the
> goal of the project, though. In particular:
> 
>   - I'm not clear what we'd hope to gain. I.e., what richer information
>     would we want to pass back and forth between index-pack and the
>     other processes? It might also be more efficient, but I'm not sure
>     it's measurably so (we save a single process, and we save some pipe
>     traffic, but the sideband demuxer would probably end up passing it
>     over a self-pipe anyway).

I didn't have any concrete ideas so I didn't include those, but some
unrefined ideas:

 - index-pack has the CLI option to specify a message to be written into
   the .promisor file, but in my patch to write fetched refs to
   .promisor [1], I ended up making fetch-pack.c write the information
   because I didn't know how many refs were going to be written (and I
   didn't want to bump into CLI argument length limits). If we had this
   feature, I might have been able to pass a callback to index-pack that
   writes the list of refs once we have the fd into .promisor,
   eliminating some code duplication (but I haven't verified this).

 - In your reply [2] to the above [1], you mentioned the possibility of
   keeping a list of cutoff points. One way of doing this, as I state in
   [3], is my original suggestion back in 2017 of one such
   repository-wide list. If we do this, it would be better for
   fetch-pack to handle this instead of index-pack, and it seems more
   efficient to me to have index-pack be able to pass objects to
   fetch-pack as they are inflated instead of fetch-pack rereading the
   compressed forms on disk (but again, I haven't verified this).

[1] https://public-inbox.org/git/20190826214737.164132-1-jonathantanmy@google.com/
[2] https://public-inbox.org/git/20190905070153.GE21450@sigill.intra.peff.net/
[3] https://public-inbox.org/git/20190905183926.137490-1-jonathantanmy@google.com/

There are also the debuggability improvements of not having to deal with
2 processes.

>   - index-pack is prone to dying on bad input, and we wouldn't want it
>     to take down the outer fetch-pack or receive-pack, which are what
>     produce useful messages to the user. That's something that could be
>     fixed as part of the libification, but I suspect the control flow
>     might be a little tricky.

Good point.

>   - we don't always call index-pack, but sometimes call unpack-objects.
>     I suppose we could continue to call an external unpack-objects in
>     that path, but that eliminates the utility of having richer
>     communication if we sometimes have to take the "dumb" path. A while
>     ago I took a stab at teaching index-pack to unpack. It works, but
>     there are a few ugly bits, as discussed in:
> 
>       https://github.com/peff/git/commit/7df82454a855281e9c147f3023225f8a6f72e303
> 
>     Maybe that would be worth making part of the project?

I'm reluctant to do so because I don't want to increase the scope too
much - although if my project has relatively narrow scope for an
Outreachy project, we can do so. As for eliminating the utility of
having richer communication, I don't think so, because in the situations
where we require richer communication (right now, situations to do with
partial clone), we specifically run index-pack anyway.

  reply	other threads:[~2019-09-23 20:39 UTC|newest]

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-27  5:17 Jeff King
2019-08-31  7:58 ` Christian Couder
2019-08-31 19:44   ` Olga Telezhnaya
2019-09-04 19:41 ` Jeff King
2019-09-05  7:24   ` Christian Couder
2019-09-05 19:39   ` Emily Shaffer
2019-09-06 11:55     ` Carlo Arenas
2019-09-07  6:39       ` Jeff King
2019-09-07 10:13         ` Carlo Arenas
2019-09-07  6:36     ` Jeff King
2019-09-08 14:56   ` Pratyush Yadav
2019-09-09 17:00     ` Jeff King
2019-09-23 18:07   ` SZEDER Gábor
2019-09-26  9:47     ` SZEDER Gábor
2019-09-26 19:32       ` Johannes Schindelin
2019-09-26 21:54         ` SZEDER Gábor
2019-09-26 11:42     ` Johannes Schindelin
2019-09-13 20:03 ` Jonathan Tan
2019-09-13 20:51   ` Jeff King
2019-09-16 18:42     ` Emily Shaffer
2019-09-16 21:33       ` Eric Wong
2019-09-16 21:44       ` SZEDER Gábor
2019-09-16 23:13         ` Jonathan Nieder
2019-09-17  0:59           ` Jeff King
2019-09-17 11:23       ` Johannes Schindelin
2019-09-17 12:02         ` SZEDER Gábor
2019-09-23 12:47           ` Johannes Schindelin
2019-09-23 16:58             ` SZEDER Gábor
2019-09-26 11:04               ` Johannes Schindelin
2019-09-26 13:28                 ` SZEDER Gábor
2019-09-26 19:39                   ` Johannes Schindelin
2019-09-26 21:44                     ` SZEDER Gábor
2019-09-27 22:18                       ` Jeff King
2019-10-09 17:25                         ` SZEDER Gábor
2019-10-11  6:34                           ` Jeff King
2019-09-23 18:19             ` Jeff King
2019-09-24 14:30               ` Johannes Schindelin
2019-09-17 15:10         ` Christian Couder
2019-09-23 12:50           ` Johannes Schindelin
2019-09-23 19:30           ` Jeff King
2019-09-23 18:07         ` Jeff King
2019-09-24 14:25           ` Johannes Schindelin
2019-09-24 15:33             ` Jeff King
2019-09-28  3:56               ` Junio C Hamano
2019-09-24  0:55         ` Eric Wong
2019-09-26 12:45           ` Johannes Schindelin
2019-09-30  8:55             ` Eric Wong
2019-09-28  4:01           ` Junio C Hamano
2019-09-20 17:04     ` Jonathan Tan
2019-09-21  1:47       ` Emily Shaffer
2019-09-23 14:23         ` Christian Couder
2019-09-23 19:40         ` Jeff King
2019-09-23 22:29           ` Philip Oakley
2019-10-22 21:16         ` Emily Shaffer
2019-09-23 11:49       ` Christian Couder
2019-09-23 17:58         ` Jonathan Tan
2019-09-23 19:27           ` Jeff King
2019-09-23 20:48             ` Jonathan Tan
2019-09-23 19:15       ` Jeff King
2019-09-23 20:38         ` Jonathan Tan [this message]
2019-09-23 21:28           ` Jeff King
2019-09-24 17:07             ` Jonathan Tan
2019-09-26  7:09               ` Jeff King

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