Messages in this thread | | | Date | Wed, 16 Jan 2013 18:32:09 +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 09:55, Soeren Moch wrote: > On 16.01.2013 04:24, Soeren Moch wrote: >> 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. >>> > OK, I could trigger the error > ERROR: 1024 KiB atomic DMA coherent pool is too small! > Please increase it with coherent_pool= kernel parameter! > only with em28xx sticks and sata, dib0700 sticks removed. > >>> Just out of curiosity, what board is it? >> >> The kirkwood board? A modified Guruplug Server Plus. > em28xx sticks: "TerraTec Cinergy HTC Stick HD" and "PCTV Quatro Stick" > dib0700 sticks: "WinTV-NOVA-TD Stick" >>> >>>> 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 don't want to say that Mareks patch is wrong, probably it triggers a > bug somewhere else! (in em28xx?)
The em28xx sticks are using isochronous usb transfers. Is there a special handling for that?
>> 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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