Re: [PATCH 00/46] Based on latest mm-unstable (85b44c25cd1e).

[David Hildenbrand]

On 09.01.23 20:53, Mike Kravetz wrote:
> On 01/05/23 11:47, David Hildenbrand wrote:
> > On 05.01.23 11:17, James Houghton wrote:
> > > This series introduces the concept of HugeTLB high-granularity mapping
> > > (HGM). This series teaches HugeTLB how to map HugeTLB pages at
> > > high-granularity, similar to how THPs can be PTE-mapped.
> > >
> > > Support for HGM in this series is for MAP_SHARED VMAs on x86 only. Other
> > > architectures and (some) support for MAP_PRIVATE will come later.
> >
> > Why even care about the complexity of COW-sharable anon pages? TBH, I'd just
> > limit this to MAP_SHARED and call it a day. Sure, we can come up with use
> > cases for everything (snapshotting VMs using fork while also support
> > optimized postcopy), but I think this would need some real justification for
> > the added complexity and possible (likely!) issues.
>
> I believe the primary use case driving this beyond MAP_SHARED would be
> poisoning due to memory errors.  Extending HGM seems to be the most
> elegant way to start providing better support for this.

Good point. Although I wonder if in practice, most applicable users 
either already are, or should switch to, using MAP_SHARED hugetlb.

--
Thanks,

David / dhildenb