bug#24143: 25.1; Windows performace of process-send-string

[Eli Zaretskii <eliz@gnu.org>]

tags 24143 + notabug
thanks

> Date: Thu, 4 Aug 2016 11:40:20 +0000 (UTC)
> From: Bogdan Sirb <bogdans91@yahoo.com>
> Cc: "24143@debbugs.gnu.org" <24143@debbugs.gnu.org>
> 
> Emacs 24.5 was the one found in the repository of msys2 found
> https://msys2.github.io/ I also tried the standard one found on emacs website
> and the results were the same.

That doesn't tell how it was compiled.  My idea was that when
comparing performance of two versions, one should make sure both
builds used similar compilation switches, otherwise you could see all
kinds of strange disparities.

> But doing a (setq w32-pipe-buffer-size (* 10 4096)) fixed the problem.

Great, so I'm closing this bug.

> Now I have the following:
> 
> * emacs 24.5: 0.037496
> * emacs 25.1: 0.040418
> 
> But, if I'm doing a (setq w32-pipe-buffer-size (point-max)) to send the whole
> file at once once, I get a stunning 0.0010007 per call.
> 
> Is there any implications to doing this ?

It depends on what program is on the other end of the pipe.  Some
programs don't like large writes down the pipe.  See bug#22344, where
such large writes caused a catastrophic failure.  Emacs prefers to err
on the safe side by default, and leave any fine-tuning of the pipe
size to applications that need it.

Thanks.