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

Andrew Morton
2012-11-20T19:33:28Z

On Tue, 20 Nov 2012 15:31:45 +0100
Marek Szyprowski <m.szyprowski@samsung.com> 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?