Fwd: Running process filters in another thread

[yyoncho]

+emacs-devel

---------- Forwarded message ---------
From: yyoncho <address@hidden>
Date: Sat, Sep 29, 2018 at 12:39 AM
Subject: Re: Running process filters in another thread
To: <address@hidden>

Hi Eli,

Thanks for the quick response!

Excuse me if I am talking nonsense - my understanding is that there are Emacs threads(the threads that are available using elisp code) which run cooperatively and there are OS level threads which for example read the output of a process and then pass it to the filter function as a string and they might run in parallel and I was talking about running the pre-filter function into such thread. 

If this is not the case, I guess it won't be easy to spawn new os thread and run eventually *pure* function to process the output?

Alternatively, I was thinking about creating some faster emacs specific binary serialization/deserialization of data structures so elisp programmers could move the parsing into separate emacs instance(ala https://github.com/jwiegley/emacs-async) and then consume the output. 

Thanks,

Ivan

On Sat, Sep 29, 2018 at 12:14 AM Eli Zaretskii <address@hidden> wrote:

> From: yyoncho <address@hidden>
> Date: Fri, 28 Sep 2018 21:21:23 +0300
>
> I want to raise this topic regarding the rise of Language servers and the performance
> problems that are related to parsing process output on UI thread.
>
> I am not familiar with emacs internals and I am not sure whether this is doable
> but I wonder whether providing the option to do the parsing(and probably more?)
> in a separate thread and then call the *filter* function on emacs side in UI
> thread with elisp data structures like lists, hashmaps etc. instead of raw
> string is feasible which would be similar to what is happening in _javascript_ world.

Emacs threads are cooperative, and only one thread can run at any
given time.  So it i's unclear to me how running process filters in a
separate thread will help improve the performance in this case,
because Emacs will still be locked up when that other thread runs the
filter.

Or am I missing something?