On Tue, Nov 20, 2012 at 11:33:25AM -0800, Andrew Morton wrote: > On Tue, 20 Nov 2012 15:31:45 +0100 > Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> 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. > > > > Is this problem serious enough to justify merging the patch into 3.7? > And into -stable kernels? kirkwood and orion5x currently have the following code in their early init: /* * Some Kirkwood devices allocate their coherent buffers from atomic * context. Increase size of atomic coherent pool to make sure such the * allocations won't fail. */ init_dma_coherent_pool_size(SZ_1M); We have a pending patch to do the same for mvebu (new armv7 Marvell SoCs). There is at least one reported real world case where even the above isn't sufficient [1]. thx, Jason. [1] http://www.spinics.net/lists/arm-kernel/msg205495.html -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>