On Thu, 17 Sep 2026, Christian K�nig wrote:
On 9/16/26 18:22, Davidlohr Bueso wrote:
On Wed, 16 Sep 2026, T.J. Mercier wrote:
I'm not sure these patches were motivated by Android (based on x86
focus in the commit message), but Davidlohr would have to comment on
that. That's just where most of my experience comes from and what I
can share details about.
This series was motivated by exploring new use cases for dma-buf (such
as kvcache), not really for Android specifically. I was counting on
the cheap/one-time 2Mb attempt (current high order semantics) to not be
a problem for potential performance gains. As for the x86 I tested here,
basically because it's what I have on hand, I had no idea ROCm was a no-no
for system heaps.
Well the problem is that it does work, but gives you unstable performance and
people see that as a bug while it is an intentional design decision made to
keep the system heap driver independent.
So yeah it's a trade off, it should just be properly documented.
I am fine dropping this effort.
It's clearly good that we talked about this.
When something is changed here I would rather say that we have some #ifdef
CONFIG_ARM around the existing code and use the PMD_SIZE for all other
platforms.
Just able to circle back to this, sorry for the delay.
I will go ahead then and add the ifdefiry for arm to leave it alone, and add
the PMD size otherwise.
If functionality isn't changed I think adding at least some notes that this
only works optimal on 4k ARM platforms is clearly a good idea.
(will also comment the situation).
Thanks,
Davidlohr
