RE: Background page clearing

[Wilco Dijkstra <Wilco.Dijkstra@arm.com>]

> On 07/25/2014 08:06 AM, Wilco Dijkstra wrote:
> > Is there a reason Linux does not do background page clearing like other OSes to reduce this
> > overhead? It would be a good fit for typical mobile workloads (bursts of high activity
> followed by
> > periods of low activity).
>
> If the page is being allocated, it is about to be used and be brought in
> to the CPU's cache.  If we zero it close to this use, we only pay to
> bring it in to the CPU's cache once.  Or so goes the theory...

I can see the reasoning for 4KB pages and small allocations (eg. stack),
but would that ever be true for huge pages?

> I tried a zero-on-free implementation a year or so ago.  It helped some
> workloads and hurt others.  The gains were not large enough or
> widespread enough to merit pushing it in to the kernel.

Was that literally zero-on-free or zero in the background? Was the result
the same for different page sizes? My guess is that the result will be
different for huge pages.

Wilco

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