Re: [PATCH] add a clear_pages function to clear pages of higher order

[Andi Kleen <ak@muc.de>]

> Andi Kleen (iirc) says that non-temporal stores seem to be
> big win in microbenchmarks (and I second that), but they are
> a net loss when we are going to use zeroed page just after
> zeroing. He recommends avoid using non-temporal stores

The rule of thumb is to only use non temporal stores when your
data set is bigger than the L2/L3 caches of the CPU. This means >1MB.
The kernel normally never works on data sets that big.

For Christophers new background cleaner daemon it may be worth it 
when the queue is a LILO. This means it is likely there is a relatively
long time between the clearing operation and a workload using it.
But even then it is a very close call and would need clear benchmark 
numbers in macrobenchmarks.

-Andi