On Thu, Aug 03, 2023 at 08:45:54AM -0700, Linus Torvalds wrote:
> On Thu, 3 Aug 2023 at 02:53, Mateusz Guzik <mjguzik@xxxxxxxxx> wrote:
> >
> > So yes, atomics remain expensive on x86-64 even on a very moden uarch
> > and their impact is measurable in a syscall like read.
>
> Well, a patch like this should fix it.
>
> I intentionally didn't bother with the alpha osf version of readdir,
> because nobody cares, but I guess we could do this in the header too.
>
> Or we could have split the FMODE_ATOMIC_POS bit into two, and had a
> "ALWAYS" version and a regular version, but just having a
> "fdget_dir()" made it simpler.
>
> So this - together with just reverting commit 20ea1e7d13c1 ("file:
> always lock position for FMODE_ATOMIC_POS") - *should* fix any
> performance regression.
>
> But I have not tested it at all. So....
Yeah, this is my suggestion - and your earlier suggestion - in the
thread. Only thing that's missing is exclusion with seek on directories
as that's the heinous part.
