Re: [PATCH v9 3/3] mm: Maintain randomization of page free lists

[Dan Williams]

On Wed, Jan 30, 2019 at 11:11 AM Michal Hocko <mhocko@xxxxxxxxxx> wrote:
>
> On Tue 29-01-19 21:02:26, Dan Williams wrote:
> > When freeing a page with an order >= shuffle_page_order randomly select
> > the front or back of the list for insertion.
> >
> > While the mm tries to defragment physical pages into huge pages this can
> > tend to make the page allocator more predictable over time. Inject the
> > front-back randomness to preserve the initial randomness established by
> > shuffle_free_memory() when the kernel was booted.
> >
> > The overhead of this manipulation is constrained by only being applied
> > for MAX_ORDER sized pages by default.
>
> I have asked in v7 but didn't get any response. Do we really ned per
> free_area random pool? Why a global one is not sufficient?

Ah, yes, sorry, overlooked that feedback. A global one is sufficient.
Will rework.