Messages in this thread Patch in this message | | | From | Akinobu Mita <> | Subject | [PATCH 2/2] intel-iommu: don't unnecessarily call dma_alloc_from_contiguous() | Date | Mon, 29 Sep 2014 00:52:04 +0900 |
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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 <akinobu.mita@gmail.com> Reported-by: Peter Hurley <peter@hurleysoftware.com> Cc: Peter Hurley <peter@hurleysoftware.com> Cc: Marek Szyprowski <m.szyprowski@samsung.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Don Dutile <ddutile@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: x86@kernel.org Cc: iommu@lists.linux-foundation.org --- 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
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