Re: Anticipatory prefaulting in the page fault handler V1

Nick Piggin
2004-12-09T11:32:38Z

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.