linux-kernel - Re: malloc() size in CMA region seems to be aligned to CMA

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Message-ID: <20160518084824.GA21680@dhcp22.suse.cz>
Date:	Wed, 18 May 2016 10:48:25 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	lunar12 lunartwix <lunartwix@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Minchan Kim <minchan@...nel.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: malloc() size in CMA region seems to be aligned to CMA_ALIGNMENT

[CC linux-mm and some usual suspects]

On Tue 17-05-16 23:37:55, lunar12 lunartwix wrote:
> A 4MB dma_alloc_coherent  in kernel after malloc(2*1024) 40 times in
> CMA region by user space will cause an error on our ARM 3.18 kernel
> platform with a 32MB CMA.
> 
> It seems that the malloc in CMA region will be aligned to
> CMA_ALIGNMENT everytime even if the requested malloc size is very
> small so the CMA region is not available after the malloc operations.
> 
> Is there any configuraiton that can change this behavior??
> 
> Thanks
> 
> Cheers
> Ken

-- 
Michal Hocko
SUSE Labs