My gut feeling is that this all-new jobs/channels stuff in core vim (which I've not had a chance to look at much since it doesn't interest me) is causing the backend vim process that MacVim runs to do things that stimulate messages to our frontend process at times where we didn't expect them, resulting in sadness.

the root cause is, I guess, NetBeans support in MacVim. It has not been maintained anymore. And I'm the author of the patch😄 . I'll remove it and test it.

Fixed in #278, but still make test with $(VIMPROG) -g sometimes fails a few of tests.

I tested again with MacVim 7.4.1825 built via Homebrew.

• I never get any messages in :messages.
• Sometimes the channel log shows the output of the ls in the job; usually it doesn't.
• The close_cb handler is never called.
• The CPU processes remain low, as expected.

The log looks like this when the job's output is logged:

==== start log session ====
  0.000030 : Starting job: ls
  0.000082 on 0: Created channel
  0.014462 RECV on 0: 'Capfile
Gemfile
Gemfile.lock
README
Rakefile
app
channel.log
config
config.ru
db
demo.vim
doc
features
lib
log
private
public
script
spec
test
tmp
vendor
'
  0.014508 ERR on 0: MMChannel_read(): Cannot read from channel
  0.014528 on 0: Closing channel

And like this when the job's output isn't logged:

$ cat channel.log
==== start log session ====
  0.000030 : Starting job: ls
  0.000065 on 0: Created channel
  0.018400 ERR on 0: MMChannel_read(): Cannot read from channel
  0.018431 on 0: Closing channel

Using mvim -v ... everything works as expected.

Having said all that, when I run jobs asynchronously in vim-gitgutter with the MacVim GUI, they now work :)

I have no idea about your demo.vim is correct or not. At least, current master has no issues in src/testdir/test_channel.vim.

I was having the same problem, and it persists for me on master.

I noticed this with the "dein" plugin manager when trying to update plugins. In the GUI, the first eight jobs get started (invoking git), but no job reports results, so the updating stalls at that point. It works fine in the terminal (and in gVim on Windows, too). The logs look pretty much like those posted by airblade.

I confirm this solves the problem for me. Thank you!