On Wed, 10 Oct 2007, Nick Piggin wrote:
>
> It just seems like now might be a good time to just _try_ removing
> the zero page
Yes. Let's do your patch immediately after the x86 merge, and just see if
anybody screams.
It might take a while, because I certainly agree that whoever would be
affected by it is likely to be unusual.
> OK, maybe this is where we are not on the same page.
> There are 2 issues really. Firstly, performance problem of
> refcounting the zero-page -- we've established that it causes
> this livelock and that we should stop refcounting it, right?
Yes, I do agree that refcounting is problematic.
> Second issue is the performance difference between removing the
> zero page completely, and de-refcounting it (it's obviously
> incorrect to argue for zero page removal for performance reasons
> if the performance improvement is simply coming from avoiding
> the refcounting).
Well, even if it's a "when you don't get into the bad behaviour,
performance difference is not measurable", and give a before-and-after
number for some random but interesting load. Even if it's just a kernel
compile..
Linus
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