bug#46978: 27.1; Shell mode performs extremely poorly in Linux-libre 5.10.20

[Eli Zaretskii]

> From: Mark H Weaver <mhw@netris.org>
> Date: Sat, 06 Mar 2021 21:39:54 -0500
> 
> Mark H Weaver <mhw@netris.org> writes:
> 
> > I've skimmed the list of changes between Linux 5.10.19 and 5.10.20, and
> > found these two commits that might be relevant:
> >
> > tty: implement read_iter
> > <https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v5.10.20&id=41c6f6b926d0e712d0321f8a8f6511fea748e814>
> >
> > tty: convert tty_ldisc_ops 'read()' function to take a kernel pointer
> > <https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v5.10.20&id=279e54536ddbb4dbd337fca74926b68651160043>
> >
> > These changes are also included in Linux-libre 5.11.3 (the newest
> > release), but I haven't yet tried that version.
> >
> > I'm currently building a variant of Linux-libre 5.10.20 with these two
> > commits reverted, to see if that makes the problem go away, and I will
> > report back when I have those results.
> 
> Reverting the two commits cited above fixes the problem.

So does this mean this isn't an Emacs issue, but the issue with that
kernel?  Or is there still something you'd like us to look into on the
Emacs side?

Thanks.