linux-kernel - Re: [PATCH] mm: dmapool: use provided gfp flags for all dma_alloc

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Message-ID: <50A0D764.204@web.de>
Date:	Mon, 12 Nov 2012 12:03:00 +0100
From:	Soeren Moch <smoch@....de>
To:	Andrew Lunn <andrew@...n.ch>
CC:	Marek Szyprowski <m.szyprowski@...sung.com>,
	linux-arm-kernel@...ts.infradead.org,
	linaro-mm-sig@...ts.linaro.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Arnd Bergmann <arnd@...db.de>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Subject: Re: [PATCH] mm: dmapool: use provided gfp flags for all dma_alloc_coherent()
 calls

On 12.11.2012 11:38, Andrew Lunn wrote:
> On Mon, Nov 12, 2012 at 10:48:02AM +0100, Soeren Moch wrote:
>> On 11.11.2012 18:22, Andrew Lunn wrote:
>>> On Thu, Nov 08, 2012 at 07:38:57AM +0100, Marek Szyprowski wrote:
>>>> dmapool always calls dma_alloc_coherent() with GFP_ATOMIC flag,
>> regardless
>>>> the flags provided by the caller. This causes excessive pruning of
>>>> emergency memory pools without any good reason. This patch
>> changes the code
>>>> to correctly use gfp flags provided by the dmapool caller. This should
>>>> solve the dmapool usage on ARM architecture, where GFP_ATOMIC DMA
>>>> allocations can be served only from the special, very limited
>> memory pool.
>>>> Reported-by: Soren Moch <smoch@....de>
>> Please use
>> Reported-by: Soeren Moch <smoch@....de>
>>
>>>> Reported-by: Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
>>>> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
>>> Tested-by: Andrew Lunn <andrew@...n.ch>
>>>
>>> I tested this on a Kirkwood QNAP after removing the call to
>>> init_dma_coherent_pool_size().
>>>
>>>      Andrew
>> Tested-by: Soeren Moch <smoch@....de>
>>
>> Now I had a chance to test this patch on my Kirkwood guruplug
>> system with linux-3.6.6 . It is running much better now, but with the
>> original 256K coherent pool size I still see errors after several hours
>> of runtime:
>>
>> Nov 12 09:42:32 guru kernel: ERROR: 256 KiB atomic DMA coherent pool
>> is too small!
>> Nov 12 09:42:32 guru kernel: Please increase it with coherent_pool=
>> kernel parameter!
> Hi Soeren
>
> Could you tell us what DVB devices you are using.
>
> Thanks
> 	Andrew

from lsusb:
Bus 001 Device 005: ID 0ccd:00b2 TerraTec Electronic GmbH
Bus 001 Device 006: ID 2040:5200 Hauppauge
Bus 001 Device 009: ID 2304:0242 Pinnacle Systems, Inc.

If you want to check the drivers, I recommend to start with "em28xx".

Regards,
Soeren
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