Re: + mm-revert-thp-make-madv_hugepage-check-for-mm-def_flags.patch added to -mm tree

[Oleg Nesterov]

On 02/26, Gerald Schaefer wrote:
>
> On Wed, 26 Feb 2014 19:06:03 +0100
> Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
>
> > It would be nice to also change thp_split_mm() to not not play with
> > mm->def_flags, but I am not sure if we can do this.
>
> Hmm, I'm also wondering about this. Basically, we only need VM_NOHUGEPAGE
> in vma->vm_flags, which is done for all existing vmas in thp_split_mm().
> But if there should be new vmas created afterwards, it would still be
> necessary to also have VM_NOHUGEPAGE in mm->def_flags, because the
> vm_flags for new vmas will be set via OR of mm->def_flags, e.g. in
> do_brk() and do_mmap_pgoff().

Yes, exactly, this was my concern.

And while I know nothing about s390, it seems to me that huge pages should
be forbidden for any vma if ->has_pgste was set.

> Anyway, this would then have to be a separate patch, to keep the
> "revertability" of this hack.

Agreed. Thanks!

Oleg.

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