Re: [RFC PATCH] mm/page_alloc: Add PCP list for THP CMA

[David Hildenbrand]

On 29.07.25 14:30, akash.tyagi wrote:
> On Fri, 25 Jul 2025 at 10:27, Zi Yan <ziy@xxxxxxxxxx> wrote:
> > But there is this known problem that CMA can fail temporarily due to
> > short-term pinnings. See the "reliable CMA" work (don't remember the exact name).
> > I think you mean Guaranteed CMA[1].
> >
> > [1] https://lore.kernel.org/linux-mm/CAJuCfpEWVEqsivd7oTvp4foEho_HaD1XNP8KTeKWzG_X2skfGQ@xxxxxxxxxxxxxx/
> >
> > Best Regards,
> > Yan, Zi
>
>
> Hi,
>
> Yes, the issue I described is actually related to Guaranteed CMA[1].
>
> I have rewritten our problem statement to address concerns more specifically related to the Android common kernels.
>
> Problem statement:
> Android Common kernels usually have an out-of-tree patch to prevent file-backed page allocated from CMA.
> It allows some allocations which have lower chance of being pinned to use CMA to improve CMA utilization controlled by a flag __GFP_CMA.
> https://lore.kernel.org/lkml/cover.1604282969.git.cgoldswo@xxxxxxxxxxxxxx/
>
>
> Additionally, android kernels create cma pcp list for pages less than PAGE_ALLOC_COSTLY_ORDER, but not for THP pages.

I'm afraid you have to fix this in the android kernels.

--
Cheers,

David / dhildenb