On Wed, Sep 14, 2016 at 2:40 PM, Raslan, KarimAllah <karah...@amazon.de> wrote: > > > On 6/20/16, 10:23 AM, "Michal Hocko" <mho...@kernel.org> wrote: > > On Sat 18-06-16 12:11:19, KarimAllah Ahmed wrote: > > When sparse memory model is used an array of memory sections is created > to > > track each block of contiguous physical pages. Each element of this > array > > contains PAGES_PER_SECTION pages. During the creation of this array the > actual > > boundaries of the memory block is lost, so the whole block is either > considered > > as present or not. > > > > pfn_valid() in the sparse memory configuration checks which memory > sections the > > pfn belongs to then checks whether it's present or not. This yields > sub-optimal > > results when the available memory doesn't cover the whole memory > section, > > because pfn_valid will return 'true' even for the unavailable pfns at > the > > boundaries of the memory section. > > Please be more verbose of _why_ the patch is needed. Why those > "sub-optimal results" matter? > > Does this make sense to you ?
[ channeling my inner akpm ] What's the user visible effect of this change? What code is getting tripped up by pfn_valid() being imprecise, and why is changing pfn_valid() the preferred fix?
