* Linus Torvalds <torva...@linux-foundation.org> wrote:
> On Sun, Dec 1, 2013 at 8:55 AM, Ingo Molnar <mi...@kernel.org> wrote:
> >
> > Keeping the page invariant would bring significant performance
> > advantages to hashing.
>
> Or not. Rather, it would make things much worse. The virtual address
> is much simpler and better to avoid needing any page table lookup
> etc crap. The key is just the mm and the virtual address, and no
> silly page table walks etc necessary.
In theory the CPU could give us the phyisical page address, as the TLB
is already there: for most futex ops when the kernel runs we just
attempted access of the virtual address on the user-space side, so the
hardware already did the hard work of looking up everything in the
page tables and has it cached most likely.
But yeah, you are right :-/
Thanks,
ngo
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