linux-kernel - Re: [PATCH v2] mm: dmapool: use provided gfp flags for all dma_alloc

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Date:	Mon, 28 Jan 2013 21:59:18 +0100
From:	Soeren Moch <smoch@....de>
To:	Andrew Lunn <andrew@...n.ch>
CC:	Arnd Bergmann <arnd@...db.de>, Jason Cooper <jason@...edaemon.net>,
	Greg KH <gregkh@...uxfoundation.org>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-kernel@...r.kernel.org, Michal Hocko <mhocko@...e.cz>,
	linux-mm@...ck.org, Kyungmin Park <kyungmin.park@...sung.com>,
	Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	linaro-mm-sig@...ts.linaro.org,
	linux-arm-kernel@...ts.infradead.org,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Subject: Re: [PATCH v2] mm: dmapool: use provided gfp flags for all dma_alloc_coherent()
 calls

On 23.01.2013 19:10, Andrew Lunn wrote:
>>>>
>>>
>>> Now (in the last hour) stable, occasionally lower numbers:
>>> 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396
>>> 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396
>>> 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396
>>> 3396 3396 3396 3396 3396 3396 3396 3396 3396 3365 3396 3394 3396 3396
>>> 3396 3396 3373 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396
>>> 3396 3353 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396
>>> 3394 3396 3396 3396 3396 3396 3396 3396
>>>
>>> Before the last pool exhaustion going down:
>>> 3395 3395 3389 3379 3379 3374 3367 3360 3352 3343 3343 3343 3342 3336
>>> 3332 3324 3318 3314 3310 3307 3305 3299 3290 3283 3279 3272 3266 3265
>>> 3247 3247 3247 3242 3236 3236
>>>
>> Here I stopped vdr (and so closed all dvb_demux devices), the number
>> was remaining the same 3236, even after restart of vdr (and restart
>> of streaming).
>
> So it does suggest a leak. Probably somewhere on an error path,
> e.g. its lost video sync.
>

Now I activated the debug messages in em28xx. From the messages I see no 
correlation of the pool exhaustion and lost sync. Also I cannot see any 
error messages from the em28xx driver.
I see a lot of init_isoc/stop_urbs (maybe EPG scan?) without draining 
the coherent pool (checked with 'cat /debug/dma-api/num_free_entries', 
which gave stable numbers), but after half an hour there are only 
init_isoc messages without corresponding stop_urbs messages and 
num_free_entries decreased until coherent pool exhaustion.

Any idea where the memory leak is? What is allocating coherent buffers 
for orion-ehci?

   Soeren


Jan 28 20:46:03 guruvdr kernel: em28xx #0/2-dvb: Using 5 buffers each 
with 64 x 940 bytes
Jan 28 20:46:03 guruvdr kernel: em28xx #0 em28xx_init_isoc :em28xx: 
called em28xx_init_isoc in mode 2
Jan 28 20:46:03 guruvdr kernel: em28xx #1/2-dvb: Using 5 buffers each 
with 64 x 940 bytes
Jan 28 20:46:03 guruvdr kernel: em28xx #1 em28xx_init_isoc :em28xx: 
called em28xx_init_isoc in mode 2
Jan 28 20:46:23 guruvdr kernel: em28xx #0 em28xx_stop_urbs :em28xx: 
called em28xx_stop_urbs
Jan 28 20:46:23 guruvdr kernel: em28xx #1 em28xx_stop_urbs :em28xx: 
called em28xx_stop_urbs
Jan 28 20:46:24 guruvdr kernel: em28xx #0/2-dvb: Using 5 buffers each 
with 64 x 940 bytes
Jan 28 20:46:24 guruvdr kernel: em28xx #0 em28xx_init_isoc :em28xx: 
called em28xx_init_isoc in mode 2
Jan 28 20:46:24 guruvdr kernel: em28xx #1/2-dvb: Using 5 buffers each 
with 64 x 940 bytes
Jan 28 20:46:24 guruvdr kernel: em28xx #1 em28xx_init_isoc :em28xx: 
called em28xx_init_isoc in mode 2
Jan 28 20:46:44 guruvdr kernel: em28xx #1 em28xx_stop_urbs :em28xx: 
called em28xx_stop_urbs
Jan 28 20:46:44 guruvdr kernel: em28xx #0 em28xx_stop_urbs :em28xx: 
called em28xx_stop_urbs
Jan 28 20:46:45 guruvdr kernel: em28xx #1/2-dvb: Using 5 buffers each 
with 64 x 940 bytes
Jan 28 20:46:45 guruvdr kernel: em28xx #1 em28xx_init_isoc :em28xx: 
called em28xx_init_isoc in mode 2
Jan 28 20:46:45 guruvdr kernel: em28xx #0/2-dvb: Using 5 buffers each 
with 64 x 940 bytes
Jan 28 20:46:45 guruvdr kernel: em28xx #0 em28xx_init_isoc :em28xx: 
called em28xx_init_isoc in mode 2
Jan 28 20:54:33 guruvdr kernel: ERROR: 1024 KiB atomic DMA coherent pool 
is too small!
Jan 28 20:54:33 guruvdr kernel: Please increase it with coherent_pool= 
kernel parameter!

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