If CONFIG_DMA_CMA is enabled, intel_alloc_coherent() tries to allocate memory region by dma_alloc_from_contiguous() before trying to use alloc_pages().
This wastes CMA region by small DMA-coherent buffers which can be allocated by alloc_pages(). And it also causes performance degradation, as this is trying to drive _all_ dma mapping allocations through a _very_ small window, reported by Peter Hurley. This fixes it by trying to allocate by alloc_pages() first in intel_alloc_coherent() as dma_alloc_from_contiguous should be called only for huge allocation. Signed-off-by: Akinobu Mita <[email protected]> Reported-by: Peter Hurley <[email protected]> Cc: Peter Hurley <[email protected]> Cc: Marek Szyprowski <[email protected]> Cc: Konrad Rzeszutek Wilk <[email protected]> Cc: David Woodhouse <[email protected]> Cc: Don Dutile <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: Andi Kleen <[email protected]> Cc: Yinghai Lu <[email protected]> Cc: [email protected] Cc: [email protected] --- drivers/iommu/intel-iommu.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c index 3441615..f9794fa 100644 --- a/drivers/iommu/intel-iommu.c +++ b/drivers/iommu/intel-iommu.c @@ -3250,7 +3250,8 @@ static void *intel_alloc_coherent(struct device *dev, size_t size, flags |= GFP_DMA32; } - if (flags & __GFP_WAIT) { + page = alloc_pages(flags | __GFP_NOWARN, order); + if (!page && (flags & __GFP_WAIT)) { unsigned int count = size >> PAGE_SHIFT; page = dma_alloc_from_contiguous(dev, count, order); @@ -3261,10 +3262,10 @@ static void *intel_alloc_coherent(struct device *dev, size_t size, } } - if (!page) - page = alloc_pages(flags, order); - if (!page) + if (!page) { + warn_alloc_failed(flags, order, NULL); return NULL; + } memset(page_address(page), 0, size); *dma_handle = __intel_map_single(dev, page_to_phys(page), size, -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
