Subject: Re: bug#49264: 28.0.50; project.el+tramp performance issue

From: Phil Sainty <[email-masked]>
Date: Thu, 01 Jul 2021 01:25:07 +1200

On 2021-07-01 00:46, Eli Zaretskii wrote:
>> As a note here, when N files are in the same directory the normal 
>> thing
>> is that all of them share the VCS. So calling a check function for all
>> of them is redundant and slow.
> 
> AFAIR, that's not really true, and ISTR project.el aims to support the
> use cases with several different VC backends.

It's probably worth considering that while one *can* have multiple VC
backends active in a single directory, it's *extremely* common not to.

If there was a user option which effectively opted out of the multiple-
backend support in favour of performance-oriented assumptions and
caching, along with some mechanism for flushing the cache on demand
(advertised to the user as part of the user option documentation),
then users could then enable that option as a performance measure
provided that they were confident that the default functionality was
redundant for their use-cases (as I suspect it would be for many
people).

-Phil