On 30/11/2018 11:14, John Garry wrote:
From: Ganapatrao Kulkarni <ganapatrao.kulka...@cavium.com>
Hi Joerg, A friendly reminder. Can you please let me know your position on this patch? Cheers, John
Change function __iommu_dma_alloc_pages() to allocate pages for DMA from respective device NUMA node. The ternary operator which would be for alloc_pages_node() is tidied along with this. The motivation for this change is to have a policy for page allocation consistent with direct DMA mapping, which attempts to allocate pages local to the device, as mentioned in [1]. In addition, for certain workloads it has been observed a marginal performance improvement. The patch caused an observation of 0.9% average throughput improvement for running tcrypt with HiSilicon crypto engine. We also include a modification to use kvzalloc() for kzalloc()/vzalloc() combination. [1] https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1692998.html Signed-off-by: Ganapatrao Kulkarni <ganapatrao.kulka...@cavium.com> [JPG: Added kvzalloc(), drop pages ** being device local, remove ternary operator, update message] Signed-off-by: John Garry <john.ga...@huawei.com> --- Difference: v1->v2: - Add Ganapatrao's tag and change author v2->v3: - removed ternary operator - stopped making pages ** allocation local to device v3->v4: - Update commit message to include motivation for patch, including headline performance improvement for test. Some notes: This patch was originally posted by Ganapatrao in [2]. However, after initial review, it was never reposted (due to lack of cycles, I think). In addition, the functionality in its sibling patches were merged through patches, as mentioned in [2]; this also refers to a discussion on device local allocations vs CPU local allocations for DMA pool, and which is better [1]. However, as mentioned in [1], dma_alloc_coherent() uses the locality information from the device - as in direct DMA - so this patch is just applying this same policy. And from some testing, mentioned in commit message, shows marginal improvement. [2] https://lore.kernel.org/patchwork/patch/833004/ [3] https://lkml.org/lkml/2018/8/22/391 diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c index d1b0475..4afb1a8 100644 --- a/drivers/iommu/dma-iommu.c +++ b/drivers/iommu/dma-iommu.c @@ -449,20 +449,17 @@ static void __iommu_dma_free_pages(struct page **pages, int count) kvfree(pages); } -static struct page **__iommu_dma_alloc_pages(unsigned int count, - unsigned long order_mask, gfp_t gfp) +static struct page **__iommu_dma_alloc_pages(struct device *dev, + unsigned int count, unsigned long order_mask, gfp_t gfp) { struct page **pages; - unsigned int i = 0, array_size = count * sizeof(*pages); + unsigned int i = 0, nid = dev_to_node(dev); order_mask &= (2U << MAX_ORDER) - 1; if (!order_mask) return NULL; - if (array_size <= PAGE_SIZE) - pages = kzalloc(array_size, GFP_KERNEL); - else - pages = vzalloc(array_size); + pages = kvzalloc(count * sizeof(*pages), GFP_KERNEL); if (!pages) return NULL; @@ -481,10 +478,12 @@ static struct page **__iommu_dma_alloc_pages(unsigned int count, for (order_mask &= (2U << __fls(count)) - 1; order_mask; order_mask &= ~order_size) { unsigned int order = __fls(order_mask); + gfp_t alloc_flags = gfp; order_size = 1U << order; - page = alloc_pages((order_mask - order_size) ? - gfp | __GFP_NORETRY : gfp, order); + if (order_mask > order_size) + alloc_flags |= __GFP_NORETRY; + page = alloc_pages_node(nid, alloc_flags, order); if (!page) continue; if (!order) @@ -569,7 +568,8 @@ struct page **iommu_dma_alloc(struct device *dev, size_t size, gfp_t gfp, alloc_sizes = min_size; count = PAGE_ALIGN(size) >> PAGE_SHIFT; - pages = __iommu_dma_alloc_pages(count, alloc_sizes >> PAGE_SHIFT, gfp); + pages = __iommu_dma_alloc_pages(dev, count, alloc_sizes >> PAGE_SHIFT, + gfp); if (!pages) return NULL;
