Re: vc-dir operation is very slow on large git repositories in Emacs 26.1

[Alex Harsanyi]

On Fri, Jun 22, 2018 at 4:57 PM, Eli Zaretskii <address@hidden> wrote:
>> From: Alex Harsanyi <address@hidden>

>> It seems reading output from a process in Emacs is somehow limited to 64 Kb /
>> second -- I verified this with procmon.  It looks like the behavior is the
>> same in 25.2 and 26.1, it is just that in vc-dir 25.2 does not run a git
>> command that produces a lot of output.
>
> Does it help to set w32-pipe-buffer-size to some large value, like
> 16384, and/or decrease w32-pipe-read-delay?

If I set w32-pipe-read-delay to 0 the speed improvement is
significant.  On top of that, there is an additional speed
improvement if I set w32-pipe-buffer-size to 16384, I will use
both these values in my init file.  Thanks for helping me diagnose
this.

The default values on my system were 50 msec for the read delay
and 0 for the buffer size, which according to the doc string it
defaults to 4096.  The limits the maximum read speed from a pipe
to 80Kbps (probably less, since the 50 msec is the sleep time and
actual reading the data would take some time as well). These
values would be a significant impact on reading git ls-files
output.

Out of curiosity, Eli, since you mentioned that there is no
performance impact for vc-dir on your system, what values do you
use for these two variables?

Alex.


>
> Thanks.