Re: + fs-break-generic_file_buffered_read-up-into-multiple-functions.patch added to -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 27 Oct 2020 13:35:51 +0000 Matthew Wilcox <willy@infradead.org> wrote:

> On Sun, Oct 25, 2020 at 03:08:17PM -0700, akpm@linux-foundation.org wrote:
> > The patch titled
> >      Subject: mm/filemap/c: freak generic_file_buffered_read up into multiple functions
> > has been added to the -mm tree.  Its filename is
> >      fs-break-generic_file_buffered_read-up-into-multiple-functions.patch
> 
> Can we back this out?  It really makes the THP patchset unhappy.  I think
> we can do something like this afterwards, but doing it this way round is
> ridiculously hard.

Two concerns:

: On my test box, 4k buffered random reads go from ~150k to ~250k iops,
: and the improvements to big sequential reads are even bigger.

That's a big improvement!  We want that improvement.  Throwing it away
on behalf of an as-yet-unmerged feature patchset hurts.  Can we expect that
this improvement will be available post-that-patchset?  And when?

(This improvment is rather hard to believe, really - more details on the
test environment would be useful.  Can we expect that people will in
general see similar benefits or was there something special about the
testing?)

Secondly,

: This incorporates the fix for IOCB_WAITQ handling that Jens just
: posted as well

Is this (mysterious, unreferenced!) fix against v1 of Kent's patchset,
or is it against mainline?  If it's against mainline then it's
presumably first priority.  Can we please get that sent out in a
standalone form asap?