Ahmed, Karim Allah karahmed@xxxxxxxxx > On Sep 15, 2016, at 12:05 AM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > > On Wed, Sep 14, 2016 at 2:40 PM, Raslan, KarimAllah <karahmed@xxxxxxxxx> wrote: >> >> >> On 6/20/16, 10:23 AM, "Michal Hocko" <mhocko@xxxxxxxxxx> 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? I did expand the commit message in v2 of this patch to answer these questions: https://patchwork.kernel.org/patch/9190737/ Amazon Development Center Germany GmbH Berlin - Dresden - Aachen main office: Krausenstr. 38, 10117 Berlin Geschaeftsfuehrer: Dr. Ralf Herbrich, Christian Schlaeger Ust-ID: DE289237879 Eingetragen am Amtsgericht Charlottenburg HRB 149173 B -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href