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@web.de Reported-by: Thomas Petazzoni thomas.petazzoni@free-electrons.com Signed-off-by: Marek Szyprowski m.szyprowski@samsung.com Tested-by: Andrew Lunn andrew@lunn.ch Tested-by: Soeren Moch smoch@web.de
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?
thx,
Jason.
As already reported earlier this patch improved the behavior compared to linux-3.6.x and 3.7.0 (error after several ten minutes runtime), but I still see a regression compared to linux-3.5.x. With this kernel the same system with same workload runs flawlessly.
Regards, Soeren
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