Re: [RFC 00/11] Remove 'order' argument from many mm functions

Matthew Wilcox
2019-05-14T14:51:33Z

On Thu, May 09, 2019 at 02:07:55PM +0300, Kirill A. Shutemov wrote:
> On Mon, May 06, 2019 at 09:05:58PM -0700, Matthew Wilcox wrote:
> > Anyway, this is just a quick POC due to me being on an aeroplane for
> > most of today. Maybe we don't want to spend five GFP bits on this.
> > Some bits of this could be pulled out and applied even if we don't want
> > to go for the main objective. eg rmqueue_pcplist() doesn't use its
> > gfp_flags argument.
>
> I like the idea. But I'm somewhat worried about running out of bits in
> gfp_t. Is there anything preventing us to bump gfp_t to u64 in the future?

It's stored in a few structs that might not appreciate it growing,
like struct address_space. I've been vaguely wondering about how to
combine order, gfp_t and nodeid into one parameter in a way that doesn't
grow those structs, but I don't have a solid idea yet.