Re: [PATCH v3] mm/gup: Allow real explicit breaking of COW

Peter Xu
2020-08-21T02:34:45Z

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Yep. I'll run some test and update soon.

Thanks,
Peter

On Thu., Aug. 20, 2020, 18:01 Linus Torvalds <torvalds@linux-foundation.org>
wrote:

> On Thu, Aug 20, 2020 at 2:54 PM Peter Xu <peterx@redhat.com> wrote:
> >
> > I kind of prefer the new suggestion to remove code rather than adding new
> > codes. I definitely don't know enough on the side effect of it,
> especially
> > performance-wise on either ksm or swap, but... IIUC the worst case is
> we'll get
> > some perf report later on, and it seems also not hard to revert the
> patch later
> > if we want.
>
> Well, would you be willing to try this patch out?
>
> After you apply that patch, you should be able to remove the
> should_force_cow_break() games entirely, because a write to the page
> should always break cow towards the writer if there are any GUP users
> around (put another way: away from the GUP).
>
> However, to make the test meaningful, it really should do some swap
> testing too.
>
> Linus
>

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