git@vger.kernel.org list mirror (unofficial, one of many)
 help / color / mirror / code / Atom feed
From: Jeff King <peff@peff.net>
To: Jonathan Tan <jonathantanmy@google.com>
Cc: git@vger.kernel.org
Subject: Re: Git in Outreachy December 2019?
Date: Mon, 23 Sep 2019 15:15:10 -0400	[thread overview]
Message-ID: <20190923191509.GC21344@sigill.intra.peff.net> (raw)
In-Reply-To: <20190920170448.226942-1-jonathantanmy@google.com>

On Fri, Sep 20, 2019 at 10:04:48AM -0700, Jonathan Tan wrote:

> > I'm happy to discuss possible projects if anybody has an idea but isn't
> > sure how to develop it into a proposal.
> 
> I'm new to Outreachy and programs like this, so does anyone have an
> opinion on my draft proposal below? It does not have any immediate
> user-facing benefit, but it does have a definite end point.
> 
> Also let me know if an Outreachy proposal should have more detail, etc.
> 
>     Refactor "git index-pack" logic into library code
> 
>     Currently, whenever any Git code needs a pack to be indexed, it
>     needs to spawn a new "git index-pack" process, passing command-line
>     arguments and communicating with it using file descriptors (standard
>     input and output), much like an end-user would if invoking "git
>     index-pack" directly. Refactor the pack indexing logic into library
>     code callable from other Git code, make "git index-pack" a thin
>     wrapper around that library code, and (to demonstrate that the
>     refactoring works) change fetch-pack.c to use the library code
>     instead of spawning the "git index-pack" process.
> 
>     This allows the pack indexing code to communicate with its callers
>     with the full power of C (structs, callbacks, etc.) instead of being
>     restricted to command-line arguments and file descriptors. It also
>     simplifies debugging in that there will no longer be 2
>     inter-communicating processes to deal with, only 1.

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).

  - 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.

  - 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?

-Peff

  parent reply	other threads:[~2019-09-23 19:15 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 [this message]
2019-09-23 20:38         ` Jonathan Tan
2019-09-23 21:28           ` Jeff King
2019-09-24 17:07             ` Jonathan Tan
2019-09-26  7:09               ` 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

  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=20190923191509.GC21344@sigill.intra.peff.net \
    --to=peff@peff.net \
    --cc=git@vger.kernel.org \
    --cc=jonathantanmy@google.com \
    --subject='Re: Git in Outreachy December 2019?' \
    /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

Code repositories for project(s) associated with this 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).