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From: Stefan Beller <sbeller@google.com>
To: git@vger.kernel.org
Cc: peff@peff.net, gitster@pobox.com, jrnieder@gmail.com,
	johannes.schindelin@gmail.com, Jens.Lehmann@web.de,
	vlovich@gmail.com, Stefan Beller <sbeller@google.com>
Subject: [RFC PATCHv1 0/2] Parallel git submodule fetching
Date: Fri, 11 Sep 2015 16:09:52 -0700	[thread overview]
Message-ID: <1442012994-20374-1-git-send-email-sbeller@google.com> (raw)

This is a new approach to making git submodules faster without using threads.
We'll directly run commands in parallel without an intermediate thread pool.

patch 1 is fixing an error, which was hard to come by in a parallel world,
but is not much of a problem in a single-childed world.

The second patch works fine, (I'd love to hear feedback on the percieved
change of output) though it has still two edges I want to tackle:

* The fcntl call to make the pipes nonblocking is not checked for errors.
* We also need to communicate back if one process cannot spawn or such,
  i.e. the reporting for all subprocesses combined needs to added. I think
  about adding another callback which is called to finish up a child process.

Earlier attempts used a threading pool, which made the conversion very
easy as you don't need to touch lots of existing code as you would just
replace the run_command(..) call by an add_task(..). The threading pool
would abstract away the whole parallelism and its problems. It would also
have the backpressure to the main program, add_task would just not
return if there was no place left in the queue.

[1] http://www.spinics.net/lists/git/msg258435.html

Any feedback welcome!
Thanks,
Stefan

Jonathan Nieder (1):
  Sending "Fetching submodule <foo>" output to stderr

Stefan Beller (1):
  fetch: fetch submodules in parallel

 Documentation/fetch-options.txt |   7 ++
 builtin/fetch.c                 |   6 +-
 builtin/pull.c                  |   6 ++
 run-command.c                   | 144 ++++++++++++++++++++++++++++++++++++++++
 run-command.h                   |  29 ++++++++
 strbuf.c                        |  31 +++++++++
 strbuf.h                        |   1 +
 submodule.c                     |  99 +++++++++++++++++----------
 submodule.h                     |   2 +-
 t/t0061-run-command.sh          |  16 +++++
 t/t5526-fetch-submodules.sh     |  70 ++++++++++++-------
 test-run-command.c              |  23 +++++++
 12 files changed, 373 insertions(+), 61 deletions(-)

-- 
2.6.0.rc0.131.gf624c3d

next             reply	other threads:[~2015-09-11 23:10 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-09-11 23:09 Stefan Beller [this message]
2015-09-11 23:09 ` [PATCH 1/2] Sending "Fetching submodule <foo>" output to stderr Stefan Beller
2015-09-11 23:09 ` [PATCH 2/2] fetch: fetch submodules in parallel Stefan Beller
2015-09-12 19:11   ` Junio C Hamano
2015-09-14 16:46     ` Stefan Beller
2015-09-14 17:17       ` Jeff King
2015-09-14 17:47         ` Stefan Beller
2015-09-14 17:55         ` Jonathan Nieder
2015-09-14 18:07           ` Jeff King
2015-09-14 21:50             ` [PATCHv2] " Stefan Beller
2015-09-14 21:50               ` [PATCHv2] fetch: " Stefan Beller
2015-09-14 22:06               ` [PATCHv2] " Junio C Hamano
2015-09-14 17:56         ` [PATCH 2/2] fetch: " Junio C Hamano

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