Re: brd in a memdesc world

[Matthew Wilcox <willy@infradead.org>]

On Thu, Mar 14, 2024 at 12:11:18PM +0100, Hannes Reinecke wrote:
> On 3/13/24 19:28, Matthew Wilcox wrote:
> > None of those things are needed for brd's uses.  All brd needs is to
> > be able to allocate, kmap and free chunks of memory.  Unless there are
> > plans to do more than this.
> 
> The primary goal of my patchset is to make brd a test-bed for the LBS work;
> devices with a sector size larger than 4k are really hard to come
> by. But really, it's just a testbed, and I'm not sure whether there's
> a need for that in the general audience.
> I can resubmit if you want ...
> 
> As for the memory overhead, I guess it only makes a noticable difference
> when moving to hugepages, and have brd allocate hugepages only.
> But that is future work for sure.

As I said, this is talking about a memdesc future where struct page is a
mere 8 bytes and most of its contents are reserved to the MM.  At this
point, there's no extra overhead to your patch, but there would be when
we get there.

So I don't think the folio conversion is necessary, but I think
supporting larger sector sizes in brd is a worthwhile extension.