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Subject: Re: [PATCH v3 0/6] Introduce ZONE_CMA
To: Joonsoo Kim <iamjoonsoo.kim@lge.com>
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CC: Feng Tang <feng.tang@intel.com>, Andrew Morton <akpm@linux-foundation.org>,
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From: Chen Feng <puck.chen@hisilicon.com>
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Date: Tue, 21 Jun 2016 10:08:24 +0800
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On 2016/6/20 14:48, Joonsoo Kim wrote:
> On Fri, Jun 17, 2016 at 03:38:49PM +0800, Chen Feng wrote:
>> Hi Kim & feng,
>>
>> Thanks for the share. In our platform also has the same use case.
>>
>> We only let the alloc with GFP_HIGHUSER_MOVABLE in memory.c to use cma memory.
>>
>> If we add zone_cma, It seems can resolve the cma migrate issue.
>>
>> But when free_hot_cold_page, we need let the cma page goto system directly not the pcp.
>> It can be fail while cma_alloc and cma_release. If we alloc the whole cma pages which
>> declared before.
> 
> Hmm...I'm not sure I understand your explanation. So, if I miss
> something, please let me know. We calls drain_all_pages() when
> isolating pageblock and alloc_contig_range() also has one
> drain_all_pages() calls to drain pcp pages. And, after pageblock isolation,
> freed pages belonging to MIGRATE_ISOLATE pageblock will go to the
> buddy directly so there would be no problem you mentioned. Isn't it?
> 
Yes, you are right.

I mean if the we free cma page to pcp-list, it will goto the migrate_movable list.

Then the alloc with movable flag can use the cma memory from the list with buffered_rmqueue.

But that's not what we want. It will cause the migrate fail if all movable alloc can use cma memory.

If I am wrong, please correct me.

Thanks.

> Thanks.
> 
> .
>