Re: [PATCH v2] mm: dmapool: use provided gfp flags for all dma_alloc_coherent() calls

Soeren Moch
2013-01-16T00:18:20Z

On 15.01.2013 22:56, Jason Cooper wrote:
> Soeren,
>
> On Tue, Jan 15, 2013 at 03:16:17PM -0500, Jason Cooper wrote:
>> If my understanding is correct, one of the drivers (most likely one)
>> either asks for too small of a dma buffer, or is not properly
>> deallocating blocks from the per-device pool. Either case leads to
>> exhaustion, and falling back to the atomic pool. Which subsequently
>> gets wiped out as well.
>
> If my hunch is right, could you please try each of the three dvb drivers
> in turn and see which one (or more than one) causes the error?
>

In fact I use only 2 types of DVB sticks: em28xx usb bridge plus drxk
demodulator, and dib0700 usb bridge plus dib7000p demod.

I would bet for em28xx causing the error, but this is not thoroughly
tested. Unfortunately testing with removed sticks is not easy, because
this is a production system and disabling some services for the long
time we need to trigger this error will certainly result in unhappy
users.

I will see what I can do here. Is there an easy way to track the buffer
usage without having to wait for complete exhaustion?

In linux-3.5.x there is no such problem. Can we use all available memory
for dma buffers here on armv5 architectures, in contrast to newer
kernels?

Regards,
Soeren