I've been porting Ferret (a plug-in that wraps ag/ack/grep)[0] to use the new
job/channel functionality. Implementation up on GitHub[1].
I've found that reading very long lines in NL mode locks up Vim. Discovered
this while searching for a string "foobar", which basically runs `ag --vimgrep
foobar` as a job. In this particular codebase, there is a massive source map
file which is 150MB in size and is minified such that it is a single line, and
it happens to match "foobar" . This is pathological, I know, but Vim appears to
be exhibiting degenerate performance in this case. It pegs the CPU at 100% and
runs for as long as I will let it (20 minutes or more), making me suspect some
sort of quadratic growth.
Minimal repro case:
# Create pathological file
mkdir example
cd example
ruby -e "File.open('sample.txt', 'w').puts(('x' * 150_000_000) + 'foobar')"
# Inside Vim now:
func! CloseHandler(channel)
while ch_status(a:channel) == 'buffered'
echomsg ch_read(a:channel)
endwhile
endfunc
job_start('ag --vimgrep foobar',{'close_cb':'CloseHandler'})
At this point Vim locks up. Without the close handler, the command runs and
returns just fine.
For now my workaround is to set up an `~/.agignore` file so that ag doesn't
look at the dastardly sourcemap. Another thing I could try to do, but haven't
yet, is switch to "raw" mode and implement my own buffering.
I know this is not a "reasonable" workload by any means, but still seems like
it would be nice to address the degenerate perf here. I'd expect this kind of
thing to be slow, but scale basically linearly with the length of the line
being read.
Thoughts?
-Greg
[0]: https://github.com/wincent/ferret
[1]:
https://github.com/wincent/ferret/blob/7823d571df/autoload/ferret/private/async.vim
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