On 01/15/2013 05:56 PM, Jason Cooper wrote:
Greg,
I've added you to the this thread hoping for a little insight into USB
drivers and their use of coherent and GFP_ATOMIC. Am I barking up the
wrong tree by looking a the drivers?
On Mon, Jan 14, 2013 at 12:56:57PM +0100, Soeren Moch wrote:
On 20.11.2012 15:31, 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. Additionaly,
on ARM architecture any driver which is using dmapools will sooner or
later trigger the following error:
"ERROR: 256 KiB atomic DMA coherent pool is too small!
Please increase it with coherent_pool= kernel parameter!".
Increasing the coherent pool size usually doesn't help much and only
delays such error, because all GFP_ATOMIC DMA allocations are always
served from the special, very limited memory pool.
This patch changes the dmapool code to correctly use gfp flags provided
by the dmapool caller.
Reported-by: Soeren Moch<smoch@xxxxxx>
Reported-by: Thomas Petazzoni<thomas.petazzoni@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Marek Szyprowski<m.szyprowski@xxxxxxxxxxx>
Tested-by: Andrew Lunn<andrew@xxxxxxx>
Tested-by: Soeren Moch<smoch@xxxxxx>
Now I tested linux-3.7.1 (this patch is included there) on my Marvell
Kirkwood system. I still see
ERROR: 1024 KiB atomic DMA coherent pool is too small!
Please increase it with coherent_pool= kernel parameter!
after several hours of runtime under heavy load with SATA and
DVB-Sticks (em28xx / drxk and dib0700).
Could you try running the system w/o the em28xx stick and see how it
goes with v3.7.1?
Jason,
can you point out what you think we should be looking for?
I grep'd for 'GFP_' in drivers/media/usb and especially for dvb-usb
(dib0700) it looks like most of the buffers in usb-urb.c are allocated
GFP_ATOMIC. em28xx also allocates some of the buffers atomic.
If we look for a mem leak in one of the above drivers (including sata_mv),
is there an easy way to keep track of allocated and freed kernel memory?
Sebastian
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