Switching windows is slow

[tbodt]

After installing Vimade I noticed that switching between windows became much slower. It used to be instant, but I've seen it take almost a second with vimade.

[tbodt]

Did a vim profile and all of the time was spent in a call to the neovim python remote. Ran py-spy and here's the result: vimade.svg.gz

[TaDaa]

Sounds abnormal -- some questions:

• What version of neovim and which front-end -- terminal, gui, etc?
• What OS?
• Is it slow for all syntax types or just one?
• Have you tried running in a minimal init.vim/vimrc to see if its still slow? If it's not slow in a minimal vimrc, it could be something conflicting and perhaps causing multiple window checks. If you have your config available, I'll try to reproduce later.

[TaDaa]

Think I found the cause -- added a fix to the word wrap logic. If your vimrc/init.vim is the one in your profile it should work now -- feel free to reopen if you still are having issues

[tbodt]

Thanks! Yes that is my vimrc, didn't think of just pointing you there. It's much faster now but not instant, though that's probably to be expected as half the screen needs to be redrawn.

[tbodt]

It now seems to be slow because of the IPC overhead involved in computing all these matchaddpos calls. A better solution would probably be to use 'winhighlight' and :ownsyntax.

[TaDaa]

There is definitely overhead in the ipc calls, although they should all be getting grouped together either by window or by line. matchaddpos is grouped per window when its needed, but let me know if you are seeing something different.

I do like the idea of winhighlight as a nvim only approach, it could reduce/remove a lot of the logic. I'm not quite sure what the performance difference would be, but could be an interesting experiment -- even nicer if vim implemented it as well.

[tbodt]

The matchaddpos calls are grouped together, but there's a bunch of IPC in a big loop before that which doesn't seem to be grouped. Here's a profile you can load into speedscope.app, generated by running a bit of vimscript to switch windows in an infinite loop. vimade.pyspy.gz

[TaDaa]

thanks -- going to reopen / will take a look as soon as I get a chance

[TaDaa]

cleaned up a bunch related to ipc + some additional optimizations for nvim. I think its looking overall much better.

I'm paying too much for string concat and some of the looping, so I'll probably try to reduce that later. After the current changes most of the performance cost is coming from synID which has always been the case on vim. There also may be some relevant alternatives to synID on nvim that I'll have to try out later as well

[TaDaa]

couple more updates -- performance wise nvim is now slightly ahead of vim -- seems to be some benefit for using command_output over other nvim eval functions, slight enough to give nvim the edge at least.

Had some ideas for winhighlight as you suggested. At the very least we can leverage winhighlight to generated Folded and other built-in highlights that should change per window/buffer as they become inactive as requested in #26 . We can currently determine the highlights linked to built-in highlights and skip them during the matchadd phase, but the benefit would be minimal (a few ms). If the neovim team were to fully support custom highlight replacement in winhighlight it could become the potential full approach for neovim. I'm open to other ideas here, I think winhighlight could potentially work as a solution but only in the scenario where all custom highlights link to built-in highlights.

The nvim docs also recommend using :ownsyntax for overriding custom highlights, but I think I would have to generate and override the existing syntax rules, which while is possible has other issues; I originally attempted parsing :syntax during my first attempt at this plugin (before release), but because "priority" is not captured in the output, it was not possible to accurately recreate the syntax rules. Alternatively I guess the entire syntax file could be parsed and colors replaced as a separate syntax, but I suspect that it is a whole other can of worms.

[tbodt]

Just updated to the latest Vimade, and it is indeed way faster. Thanks for working on this! There is of course still room for improvement, but I think it's now fast enough for me to use as a daily driver.

[tbodt]

As for the current state of things: I did a quick benchmark with this ex command:

:echom system("date") | let i = 0 | while i < 100 | wincmd j | wincmd k | let i += 1 | endwhile | echom system("date")

This took 4 seconds for 100 loops with two window switches per loop, which is 20ms per switch. That's perceptible but not a deal breaker. For comparison, the number is about 5ms per switch with Vimade disabled.

[TaDaa]

Nice -- thanks for your input and work as well! I'll be adding improvements at some point for moving the state comparisons into vimscript and grouping ipc per buffer per tick where possible. I'm hoping with tree-sitter looming for neovim, there may be significant performance gains soon?

Closing for now, but feel free to re-open if you bump into anything.