Messages in this thread | | | Date | Wed, 07 Nov 2012 00:07:01 +0100 | From | Sören Moch <> | Subject | Re: [PATCH V2 1/4] arm: mvebu: increase atomic coherent pool size for armada 370/XP |
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>>> For Armada 370/XP we have the same problem that for the commit >>> cb01b63, so we applied the same solution: "The default 256 KiB >>> coherent pool may be too small for some of the Kirkwood devices, so >>> increase it to make sure that devices will be able to allocate their >>> buffers with GFP_ATOMIC flag" >> >> I see a regression from linux-3.5 to linux-3.6 and think there might >> be a fundamental problem >> with this patch. On my Kirkwood system (guruplug server plus) with >> linux-3.6.2 I see following >> errors and corresponding malfunction even with further increased >> (2M, 4M) pool size: >> >> Oct 19 00:41:22 guru kernel: ERROR: 4096 KiB atomic DMA coherent >> pool is too small! >> Oct 19 00:41:22 guru kernel: Please increase it with coherent_pool= >> kernel parameter! >> >> So I had to downgrade to linux-3.5 which is running without problems. >> >> I use SATA and several DVB sticks (em28xx / drxk and dib0700). > > I'm guess its the DVB sticks which are causing the problems. We have a > number of kirkwood devices with two SATA devices which had problems > until we extended the coherent_pool. The DVB sticks are probably take > more coherent RAM. There was also an issue found recently: > > http://www.spinics.net/lists/arm-kernel/msg203962.html > > That conversation has gone quiet, but that could be because the > participants are at ELCE. > > Andrew
OK, I hope this GFP flag correction will help.
Could there be a fragmentation problem in the coherent_pool with the different drivers running under heavy load? With a pool size of 1M I see this error after several minutes, with a 4M pool I see this error after several 10 minutes. Difficult to test, but not acceptable on a production system.
Soeren
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