Messages in this thread |  | | Date | Wed, 16 Jan 2013 04:24:54 +0100 | From | Soeren Moch <> | Subject | Re: [PATCH v2] mm: dmapool: use provided gfp flags for all dma_alloc_coherent() calls |
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On 16.01.2013 03:40, Jason Cooper wrote: > Soeren, > > On Wed, Jan 16, 2013 at 01:17:59AM +0100, Soeren Moch wrote: >> On 15.01.2013 22:56, Jason Cooper wrote: >>> 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. > > Just out of curiosity, what board is it?
The kirkwood board? A modified Guruplug Server Plus. > >> 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? > > DMA_API_DEBUG
OK, maybe I can try this. > >> 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? > > Were the loads exactly the same when you tested 3.5.x?
Exactly the same, yes.
>I looked at the > changes from v3.5 to v3.7.1 for all four drivers you mentioned as well > as sata_mv. > > The biggest thing I see is that all of the media drivers got shuffled > around into their own subdirectories after v3.5. 'git show -M 0c0d06c' > shows it was a clean copy of all the files. > > What would be most helpful is if you could do a git bisect between > v3.5.x (working) and the oldest version where you know it started > failing (v3.7.1 or earlier if you know it). > I did not bisect it, but Marek mentioned earlier that commit e9da6e9905e639b0f842a244bc770b48ad0523e9 in Linux v3.6-rc1 introduced new code for dma allocations. This is probably the root cause for the new (mis-)behavior (due to my tests 3.6.0 is not working anymore). I'm not very familiar with arm mm code, and from the patch itself I cannot understand what's different. Maybe CONFIG_CMA is default also for armv5 (not only v6) now? But I might be totally wrong here, maybe someone of the mm experts can explain the difference?
Regards, Soeren
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