linux-kernel - Re: [PATCH v6 2/6] mm/cma: introduce new zone, ZONE

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Message-ID: <20161107072702.GC21159@js1304-P5Q-DELUXE>
Date:   Mon, 7 Nov 2016 16:27:02 +0900
From:   Joonsoo Kim <iamjoonsoo.kim@....com>
To:     Chen Feng <puck.chen@...ilicon.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Rik van Riel <riel@...hat.com>,
        Johannes Weiner <hannes@...xchg.org>,
        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>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 2/6] mm/cma: introduce new zone, ZONE_CMA

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@vger.kernel.org/msg1263745.html

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

Thanks.