Re: [PATCH v6 2/6] mm/cma: introduce new zone, ZONE_CMA

[Chen Feng]

On 2016/11/7 15:27, Joonsoo Kim wrote:
> On Mon, Nov 07, 2016 at 03:08:49PM +0800, Chen Feng wrote:
>>
>>
>> On 2016/11/7 14:15, Joonsoo Kim wrote:
>>> On Tue, Nov 01, 2016 at 03:58:32PM +0800, Chen Feng wrote:
>>>> 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@xxxxxxxxxxxxxxx/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@xxxxxxxxxxxxxxx/msg1263745.html
> Thanks.
> 
> .
>

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