linux-kernel - Re: [PATCH v3 0/6] Introduce ZONE

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Date:	Tue, 21 Jun 2016 10:08:24 +0800
From:	Chen Feng <puck.chen@...ilicon.com>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
CC:	Feng Tang <feng.tang@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	"mgorman@...hsingularity.net" <mgorman@...hsingularity.net>,
	Laura Abbott <lauraa@...eaurora.org>,
	"Minchan Kim" <minchan@...nel.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	"Michal Nazarewicz" <mina86@...a86.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Rui Teng <rui.teng@...ux.vnet.ibm.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Yiping Xu <xuyiping@...ilicon.com>,
	"fujun (F)" <oliver.fu@...ilicon.com>,
	"Zhuangluan Su" <suzhuangluan@...ilicon.com>,
	Dan Zhao <dan.zhao@...ilicon.com>,
	<saberlily.xia@...ilicon.com>
Subject: Re: [PATCH v3 0/6] Introduce ZONE_CMA



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.
> 
> .
>