Commit 67ca1415 authored by Anton Blanchard's avatar Anton Blanchard Committed by Benjamin Herrenschmidt
Browse files

powerpc/iommu: Reduce spinlock coverage in iommu_free 



This patch moves tce_free outside of the lock in iommu_free.

Some performance numbers were obtained with a Chelsio T3 adapter on
two POWER7 boxes, running a 100 session TCP round robin test.

Performance improved 25% with this patch applied.

Signed-off-by: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 0e4bc95d

arch/powerpc/kernel/iommu.c

+40 −11
Original line number Diff line number Diff line
@@ -190,10 +190,7 @@ static dma_addr_t iommu_alloc(struct device *dev, struct iommu_table *tbl, 
	 * not altered.

	 */

	if (unlikely(build_fail)) {

		spin_lock_irqsave(&(tbl->it_lock), flags);

		__iommu_free(tbl, ret, npages);

		spin_unlock_irqrestore(&(tbl->it_lock), flags);



		return DMA_ERROR_CODE;

	}
@@ -207,7 +204,7 @@ static dma_addr_t iommu_alloc(struct device *dev, struct iommu_table *tbl, 
	return ret;

}



static void __iommu_free(struct iommu_table *tbl, dma_addr_t dma_addr, 

static bool iommu_free_check(struct iommu_table *tbl, dma_addr_t dma_addr,

			     unsigned int npages)

{

	unsigned long entry, free_entry;
@@ -228,21 +225,53 @@ static void __iommu_free(struct iommu_table *tbl, dma_addr_t dma_addr, 
			printk(KERN_INFO "\tindex     = 0x%llx\n", (u64)tbl->it_index);

			WARN_ON(1);

		}

		return;



		return false;

	}



	return true;

}



static void __iommu_free_locked(struct iommu_table *tbl, dma_addr_t dma_addr,

			 unsigned int npages)

{

	unsigned long entry, free_entry;



	BUG_ON(!spin_is_locked(&tbl->it_lock));



	entry = dma_addr >> IOMMU_PAGE_SHIFT;

	free_entry = entry - tbl->it_offset;



	if (!iommu_free_check(tbl, dma_addr, npages))

		return;



	ppc_md.tce_free(tbl, entry, npages);

	bitmap_clear(tbl->it_map, free_entry, npages);

}



static void iommu_free(struct iommu_table *tbl, dma_addr_t dma_addr,

static void __iommu_free(struct iommu_table *tbl, dma_addr_t dma_addr,

			 unsigned int npages)

{

	unsigned long entry, free_entry;

	unsigned long flags;



	entry = dma_addr >> IOMMU_PAGE_SHIFT;

	free_entry = entry - tbl->it_offset;



	if (!iommu_free_check(tbl, dma_addr, npages))

		return;



	ppc_md.tce_free(tbl, entry, npages);



	spin_lock_irqsave(&(tbl->it_lock), flags);

	__iommu_free(tbl, dma_addr, npages);

	bitmap_clear(tbl->it_map, free_entry, npages);

	spin_unlock_irqrestore(&(tbl->it_lock), flags);

}



static void iommu_free(struct iommu_table *tbl, dma_addr_t dma_addr,

		unsigned int npages)

{

	__iommu_free(tbl, dma_addr, npages);



	/* Make sure TLB cache is flushed if the HW needs it. We do

	 * not do an mb() here on purpose, it is not needed on any of
@@ -390,7 +419,7 @@ int iommu_map_sg(struct device *dev, struct iommu_table *tbl, 
			vaddr = s->dma_address & IOMMU_PAGE_MASK;

			npages = iommu_num_pages(s->dma_address, s->dma_length,

						 IOMMU_PAGE_SIZE);

			__iommu_free(tbl, vaddr, npages);

			__iommu_free_locked(tbl, vaddr, npages);

			s->dma_address = DMA_ERROR_CODE;

			s->dma_length = 0;

		}
@@ -425,7 +454,7 @@ void iommu_unmap_sg(struct iommu_table *tbl, struct scatterlist *sglist, 
			break;

		npages = iommu_num_pages(dma_handle, sg->dma_length,

					 IOMMU_PAGE_SIZE);

		__iommu_free(tbl, dma_handle, npages);

		__iommu_free_locked(tbl, dma_handle, npages);

		sg = sg_next(sg);

	}

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