Re: Anticipatory prefaulting in the page fault handler V1

[Nick Piggin]

Pavel Machek wrote:
> Hi!
>
>
> > Standard Kernel on a 512 Cpu machine allocating 32GB with an increasing
> > number of threads (and thus increasing parallellism of page faults):
> >
> > Gb Rep Threads   User      System     Wall flt/cpu/s fault/wsec
> > 32   3    1    1.416s    138.165s 139.050s 45073.831  45097.498
>
> ...
>
> > Patched kernel:
> >
> > Gb Rep Threads   User      System     Wall flt/cpu/s fault/wsec
> > 32   3    1    1.098s    138.544s 139.063s 45053.657  45057.920
>
> ...
>
> > These number are roughly equal to what can be accomplished with the
> > page fault scalability patches.
> >
> > Kernel patches with both the page fault scalability patches and
> > prefaulting:
> >
> > Gb Rep Threads   User      System     Wall flt/cpu/s fault/wsec
> > 32  10    1    4.103s    456.384s 460.046s 45541.992  45544.369
>
> ...
>
> > The fault rate doubles when both patches are applied.
>
> ...
>
> > We are getting into an almost linear scalability in the high end with
> > both patches and end up with a fault rate > 3 mio faults per second.
>
>
> Well, with both patches you also slow single-threaded case more than
> twice. What are the effects of this patch on UP system?

fault/wsec is the important number.

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