On Fri, 2 Nov 2007 19:12:27 +0200 Muli Ben-Yehuda <muli@xxxxxxxxxx> wrote: > On Sat, Nov 03, 2007 at 02:05:39AM +0900, FUJITA Tomonori wrote: > > > This patchset convert the PPC64 IOMMU to use the iova code for free > > area management. > > > > The IOMMUs ignores low level drivers' restrictions, the maximum > > segment size and segment boundary. > > > > I fixed the former: > > > > http://thread.gmane.org/gmane.linux.scsi/35602 > > > > The latter makes the free area management complicated. I'd like to > > convert IOMMUs to use the iova code (that intel-iommu introduced) > > for free area management and enable iova to handle segment boundary > > restrictions, rather than fixing all the IOMMUs' free area > > management, > > In general it sounds like a great idea, but have you looked at what > impact this has on the performance of the IO path? I converted swiotlb to use iova and compared it with the original algorithm (better than the simple bit map one that most of the IOMMUs use, I think). I use 'swiotlb=force' boot option and run netperf with "-m 128 -D" (lead to tons of dma_map_single). The original produced 281.8 Mb/s and the iova produced 77.2 Mb/s. Seems that it would be better to generalization the swiotlb algorithm (at least for small I/O area)? Or my patch might have bugs. Here's the patch to convert swiotlb to use iova against my iova patchset: http://marc.info/?l=linux-kernel&m=119402340801254&w=2 diff --git a/arch/x86/Kconfig.x86_64 b/arch/x86/Kconfig.x86_64 index c10d3f0..8735822 100644 --- a/arch/x86/Kconfig.x86_64 +++ b/arch/x86/Kconfig.x86_64 @@ -524,6 +524,7 @@ config CALGARY_IOMMU_ENABLED_BY_DEFAULT # need this always selected by IOMMU for the VIA workaround config SWIOTLB bool + select IOVA help Support for software bounce buffers used on x86-64 systems which don't have a hardware IOMMU (e.g. the current generation diff --git a/arch/x86/kernel/pci-dma_64.c b/arch/x86/kernel/pci-dma_64.c index aa805b1..8507402 100644 --- a/arch/x86/kernel/pci-dma_64.c +++ b/arch/x86/kernel/pci-dma_64.c @@ -325,6 +325,9 @@ static int __init pci_iommu_init(void) gart_iommu_init(); #endif +#ifdef CONFIG_SWIOTLB + swiotlb_alloc(); +#endif no_iommu_init(); return 0; } diff --git a/include/asm-x86/swiotlb.h b/include/asm-x86/swiotlb.h index f9c5895..f00d20c 100644 --- a/include/asm-x86/swiotlb.h +++ b/include/asm-x86/swiotlb.h @@ -40,6 +40,7 @@ extern void swiotlb_free_coherent (struct device *hwdev, size_t size, void *vaddr, dma_addr_t dma_handle); extern int swiotlb_dma_supported(struct device *hwdev, u64 mask); extern void swiotlb_init(void); +extern void swiotlb_alloc(void); extern int swiotlb_force; diff --git a/lib/swiotlb.c b/lib/swiotlb.c index 1a8050a..54ecb87 100644 --- a/lib/swiotlb.c +++ b/lib/swiotlb.c @@ -24,6 +24,7 @@ #include <linux/string.h> #include <linux/types.h> #include <linux/ctype.h> +#include <linux/iova.h> #include <asm/io.h> #include <asm/dma.h> @@ -103,10 +104,7 @@ static unsigned int io_tlb_index; */ static unsigned char **io_tlb_orig_addr; -/* - * Protect the above data structures in the map and unmap calls - */ -static DEFINE_SPINLOCK(io_tlb_lock); +static struct iova_domain swiotlb_iovad; static int __init setup_io_tlb_npages(char *str) @@ -272,6 +270,19 @@ cleanup1: return -ENOMEM; } +static struct kmem_cache *iova_cachep; + +void __init +swiotlb_alloc(void) +{ + if (!swiotlb) + return; + + iova_cachep = KMEM_CACHE(iova, 0); + init_iova_domain(&swiotlb_iovad, DMA_32BIT_MASK >> IO_TLB_SHIFT, + iova_cachep); +} + static int address_needs_mapping(struct device *hwdev, dma_addr_t addr) { @@ -288,70 +299,20 @@ address_needs_mapping(struct device *hwdev, dma_addr_t addr) static void * map_single(struct device *hwdev, char *buffer, size_t size, int dir) { - unsigned long flags; char *dma_addr; - unsigned int nslots, stride, index, wrap; + unsigned int nslots, index; int i; + struct iova *iova; - /* - * For mappings greater than a page, we limit the stride (and - * hence alignment) to a page size. - */ nslots = ALIGN(size, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT; - if (size > PAGE_SIZE) - stride = (1 << (PAGE_SHIFT - IO_TLB_SHIFT)); - else - stride = 1; - BUG_ON(!nslots); - /* - * Find suitable number of IO TLB entries size that will fit this - * request and allocate a buffer from that IO TLB pool. - */ - spin_lock_irqsave(&io_tlb_lock, flags); - { - wrap = index = ALIGN(io_tlb_index, stride); - - if (index >= io_tlb_nslabs) - wrap = index = 0; - - do { - /* - * If we find a slot that indicates we have 'nslots' - * number of contiguous buffers, we allocate the - * buffers from that slot and mark the entries as '0' - * indicating unavailable. - */ - if (io_tlb_list[index] >= nslots) { - int count = 0; - - for (i = index; i < (int) (index + nslots); i++) - io_tlb_list[i] = 0; - for (i = index - 1; (OFFSET(i, IO_TLB_SEGSIZE) != IO_TLB_SEGSIZE -1) && io_tlb_list[i]; i--) - io_tlb_list[i] = ++count; - dma_addr = io_tlb_start + (index << IO_TLB_SHIFT); - - /* - * Update the indices to avoid searching in - * the next round. - */ - io_tlb_index = ((index + nslots) < io_tlb_nslabs - ? (index + nslots) : 0); - - goto found; - } - index += stride; - if (index >= io_tlb_nslabs) - index = 0; - } while (index != wrap); - - spin_unlock_irqrestore(&io_tlb_lock, flags); + iova = alloc_iova(&swiotlb_iovad, nslots, io_tlb_nslabs - 1, 1); + if (!iova) return NULL; - } - found: - spin_unlock_irqrestore(&io_tlb_lock, flags); + index = iova->pfn_lo; + dma_addr = io_tlb_start + (index << IO_TLB_SHIFT); /* * Save away the mapping from the original address to the DMA address. * This is needed when we sync the memory. Then we sync the buffer if @@ -371,8 +332,6 @@ map_single(struct device *hwdev, char *buffer, size_t size, int dir) static void unmap_single(struct device *hwdev, char *dma_addr, size_t size, int dir) { - unsigned long flags; - int i, count, nslots = ALIGN(size, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT; int index = (dma_addr - io_tlb_start) >> IO_TLB_SHIFT; char *buffer = io_tlb_orig_addr[index]; @@ -386,30 +345,7 @@ unmap_single(struct device *hwdev, char *dma_addr, size_t size, int dir) */ memcpy(buffer, dma_addr, size); - /* - * Return the buffer to the free list by setting the corresponding - * entries to indicate the number of contigous entries available. - * While returning the entries to the free list, we merge the entries - * with slots below and above the pool being returned. - */ - spin_lock_irqsave(&io_tlb_lock, flags); - { - count = ((index + nslots) < ALIGN(index + 1, IO_TLB_SEGSIZE) ? - io_tlb_list[index + nslots] : 0); - /* - * Step 1: return the slots to the free list, merging the - * slots with superceeding slots - */ - for (i = index + nslots - 1; i >= index; i--) - io_tlb_list[i] = ++count; - /* - * Step 2: merge the returned slots with the preceding slots, - * if available (non zero) - */ - for (i = index - 1; (OFFSET(i, IO_TLB_SEGSIZE) != IO_TLB_SEGSIZE -1) && io_tlb_list[i]; i--) - io_tlb_list[i] = ++count; - } - spin_unlock_irqrestore(&io_tlb_lock, flags); + free_iova(&swiotlb_iovad, index); } static void -- 1.5.3.4 - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
