linux-kernel - Re: [PATCH 3/3] CMA: Add cma_alloc_counter to make cma

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Date:	Tue, 30 Dec 2014 14:00:38 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Hui Zhu <zhuhui@...omi.com>
Cc:	m.szyprowski@...sung.com, mina86@...a86.com,
	akpm@...ux-foundation.org, aneesh.kumar@...ux.vnet.ibm.com,
	pintu.k@...sung.com, weijie.yang@...sung.com, mgorman@...e.de,
	hannes@...xchg.org, riel@...hat.com, vbabka@...e.cz,
	laurent.pinchart+renesas@...asonboard.com, rientjes@...gle.com,
	sasha.levin@...cle.com, liuweixing@...omi.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	teawater@...il.com
Subject: Re: [PATCH 3/3] CMA: Add cma_alloc_counter to make cma_alloc work
 better if it meet busy range

On Thu, Dec 25, 2014 at 05:43:28PM +0800, Hui Zhu wrote:
> In [1], Joonsoo said that cma_alloc_counter is useless because pageblock
> is isolated.
> But if alloc_contig_range meet a busy range, it will undo_isolate_page_range
> before goto try next range. At this time, __rmqueue_cma can begin allocd
> CMA memory from the range.

Is there any real issue from this?
When failed, we will quickly re-isolate pageblock for adjacent page
so there is no big problem I guess.

If there is real issue, how about doing start_isolation/undo_isolation
in cma_alloc()? It would reduce useless do/undo isolation due to
failed trial.

Thanks.

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