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powerpc/iommu: Reduce spinlock coverage in iommu_free

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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: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Anton Blanchard 2012-06-03 19:43:44 +00:00 committed by Benjamin Herrenschmidt
parent 0e4bc95d87
commit 67ca141567
1 changed files with 41 additions and 12 deletions
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53
arch/powerpc/kernel/iommu.c
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@ -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;
}
@ -207,8 +204,8 @@ 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,
unsigned int npages)
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,
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);
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)
{
unsigned long flags;
spin_lock_irqsave(&(tbl->it_lock), flags);
__iommu_free(tbl, dma_addr, npages);
spin_unlock_irqrestore(&(tbl->it_lock), flags);
/* 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);
}