On Fri, 15 Sept 2023 at 11:37, Matthew Wilcox (Oracle)
<willy@xxxxxxxxxxxxx> wrote:
>
> I don't have any performance numbers; I'm hoping Nick might provide some
> since PPC seems particularly unhappy with write-after-write hazards.
I suspect you can't see the extra atomic in the IO paths.
The existing trick with bit #7 is because we do a lot of
page_lock/unlock pairs even when there is no actual IO. So it's worth
it because page_unlock() really traditionally shows up quite a bit.
But once you actually do IO, I think the effect is not measurable.
That said, the series doesn't look *wrong*, although I did note a few
things that just made me go "that looks very strange to me" in there.
Linus
