On 2016/11/7 15:27, Joonsoo Kim wrote:

On Mon, Nov 07, 2016 at 03:08:49PM +0800, Chen Feng wrote:

quoted

On 2016/11/7 14:15, Joonsoo Kim wrote:

quoted

On Tue, Nov 01, 2016 at 03:58:32PM +0800, Chen Feng wrote:

quoted

Hello, I hava a question on cma zone.

When we have cma zone, cma zone will be the highest zone of system.

In android system, the most memory allocator is ION. Media system will
alloc unmovable memory from it.

On low memory scene, will the CMA zone always do balance?

Allocation request for low zone (normal zone) would not cause CMA zone
to be balanced since it isn't helpful.

Yes. But the cma zone will run out soon. And it always need to do balance.

How about use migrate cma before movable and let cma type to fallback movable.

https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1263745.html

ZONE_CMA approach will act like as your solution. Could you elaborate
more on the problem of zone approach?

The ZONE approach is that makes cma pages in a zone. It can cause a higher swapin/out
than use migrate cma first.

The higher swapin/out may have a performance effect to application. The application may
use too much time swapin memory.

You can see my tested result attached for detail. And the baseline is result of [1].


[1] https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1263745.html

Thanks.

.