Re: [PATCH 1/4] mm: Trial do_wp_page() simplification

Jason Gunthorpe
2021-02-02T16:47:39Z

On Tue, Feb 02, 2021 at 11:31:27AM -0500, Peter Xu wrote:
> On Tue, Feb 02, 2021 at 04:40:33PM +0200, Gal Pressman wrote:
> > Hi Peter & Jason,
>
> Hi, Gal, Jason,
>
> >
> > It seems the hugetlb part was overlooked?
> > We're testing if the RDMA fork MADV_DONTFORK stuff can be removed on appropriate
> > kernels, but our tests still fail due to lacking explicit huge pages support [1].
>
> I didn't think it high priority only because I think most hugetlbfs users
> should be using it shared, but maybe I'm wrong.. Then it got lost indeed.

It turns out people are doing this:

mmap(NULL, SEND_BUFF_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, -1, 0)

Which makes some sense...

Gal, you could also MADV_DONTFORK this range if you are explicitly
allocating them via special mmap.

Jason