[PATCH 2/4] x86-64: Calgary - tighten up the bitmap locking

muli
2007-07-11T13:36:39Z

Currently the IOMMU table's lock protects both the bitmap and access
to the hardware's TCE table. Access to the TCE table is synchronized
through the bitmap; therefore, only hold the lock while modifying the
bitmap. This gives a yummy 10-15% reduction in CPU utilization for
netperf on a large SMP machine.

Signed-off-by: Muli Ben-Yehuda <muli@il.ibm.com>
---
arch/x86_64/kernel/pci-calgary.c | 40 ++++++++++++++++---------------------
1 files changed, 17 insertions(+), 23 deletions(-)

diff --git a/arch/x86_64/kernel/pci-calgary.c b/arch/x86_64/kernel/pci-calgary.c
index f589c2d..28ce2b3 100644
--- a/arch/x86_64/kernel/pci-calgary.c
+++ b/arch/x86_64/kernel/pci-calgary.c
@@ -235,6 +235,7 @@ static void iommu_range_reserve(struct iommu_table *tbl,
unsigned long index;
unsigned long end;
unsigned long badbit;
+ unsigned long flags;

index = start_addr >> PAGE_SHIFT;

@@ -246,6 +247,8 @@ static void iommu_range_reserve(struct iommu_table *tbl,
if (end > tbl->it_size) /* don't go off the table */
end = tbl->it_size;

+ spin_lock_irqsave(&tbl->it_lock, flags);
+
badbit = verify_bit_range(tbl->it_map, 0, index, end);
if (badbit != ~0UL) {
if (printk_ratelimit())
@@ -255,15 +258,20 @@ static void iommu_range_reserve(struct iommu_table *tbl,
}

set_bit_string(tbl->it_map, index, npages);
+
+ spin_unlock_irqrestore(&tbl->it_lock, flags);
}

static unsigned long iommu_range_alloc(struct iommu_table *tbl,
unsigned int npages)
{
+ unsigned long flags;
unsigned long offset;

BUG_ON(npages == 0);

+ spin_lock_irqsave(&tbl->it_lock, flags);
+
offset = find_next_zero_string(tbl->it_map, tbl->it_hint,
tbl->it_size, npages);
if (offset == ~0UL) {
@@ -272,6 +280,7 @@ static unsigned long iommu_range_alloc(struct iommu_table *tbl,
tbl->it_size, npages);
if (offset == ~0UL) {
printk(KERN_WARNING "Calgary: IOMMU full.\n");
+ spin_unlock_irqrestore(&tbl->it_lock, flags);
if (panic_on_overflow)
panic("Calgary: fix the allocator.\n");
else
@@ -283,17 +292,17 @@ static unsigned long iommu_range_alloc(struct iommu_table *tbl,
tbl->it_hint = offset + npages;
BUG_ON(tbl->it_hint > tbl->it_size);

+ spin_unlock_irqrestore(&tbl->it_lock, flags);
+
return offset;
}

static dma_addr_t iommu_alloc(struct iommu_table *tbl, void *vaddr,
unsigned int npages, int direction)
{
- unsigned long entry, flags;
+ unsigned long entry;
dma_addr_t ret = bad_dma_address;

- spin_lock_irqsave(&tbl->it_lock, flags);
-
entry = iommu_range_alloc(tbl, npages);

if (unlikely(entry == bad_dma_address))
@@ -306,12 +315,9 @@ static dma_addr_t iommu_alloc(struct iommu_table *tbl, void *vaddr,
tce_build(tbl, entry, npages, (unsigned long)vaddr & PAGE_MASK,
direction);

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

error:
- spin_unlock_irqrestore(&tbl->it_lock, flags);
printk(KERN_WARNING "Calgary: failed to allocate %u pages in "
"iommu %p\n", npages, tbl);
return bad_dma_address;
@@ -323,6 +329,7 @@ static void __iommu_free(struct iommu_table *tbl, dma_addr_t dma_addr,
unsigned long entry;
unsigned long badbit;
unsigned long badend;
+ unsigned long flags;

/* were we called with bad_dma_address? */
badend = bad_dma_address + (EMERGENCY_PAGES * PAGE_SIZE);
@@ -339,6 +346,8 @@ static void __iommu_free(struct iommu_table *tbl, dma_addr_t dma_addr,

tce_free(tbl, entry, npages);

+ spin_lock_irqsave(&tbl->it_lock, flags);
+
badbit = verify_bit_range(tbl->it_map, 1, entry, entry + npages);
if (badbit != ~0UL) {
if (printk_ratelimit())
@@ -348,18 +357,14 @@ static void __iommu_free(struct iommu_table *tbl, dma_addr_t dma_addr,
}

__clear_bit_string(tbl->it_map, 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);
}

static inline struct iommu_table *find_iommu_table(struct device *dev)
@@ -404,17 +409,12 @@ static void __calgary_unmap_sg(struct iommu_table *tbl,
void calgary_unmap_sg(struct device *dev, struct scatterlist *sglist,
int nelems, int direction)
{
- unsigned long flags;
struct iommu_table *tbl = find_iommu_table(dev);

if (!translate_phb(to_pci_dev(dev)))
return;

- spin_lock_irqsave(&tbl->it_lock, flags);
-
__calgary_unmap_sg(tbl, sglist, nelems, direction);
-
- spin_unlock_irqrestore(&tbl->it_lock, flags);
}

static int calgary_nontranslate_map_sg(struct device* dev,
@@ -435,7 +435,6 @@ int calgary_map_sg(struct device *dev, struct scatterlist *sg,
int nelems, int direction)
{
struct iommu_table *tbl = find_iommu_table(dev);
- unsigned long flags;
unsigned long vaddr;
unsigned int npages;
unsigned long entry;
@@ -444,8 +443,6 @@ int calgary_map_sg(struct device *dev, struct scatterlist *sg,
if (!translate_phb(to_pci_dev(dev)))
return calgary_nontranslate_map_sg(dev, sg, nelems, direction);

- spin_lock_irqsave(&tbl->it_lock, flags);
-
for (i = 0; i < nelems; i++ ) {
struct scatterlist *s = &sg[i];
BUG_ON(!s->page);
@@ -469,8 +466,6 @@ int calgary_map_sg(struct device *dev, struct scatterlist *sg,
s->dma_length = s->length;
}

- spin_unlock_irqrestore(&tbl->it_lock, flags);
-
return nelems;
error:
__calgary_unmap_sg(tbl, sg, nelems, direction);
@@ -478,7 +473,6 @@ error:
sg[i].dma_address = bad_dma_address;
sg[i].dma_length = 0;
}
- spin_unlock_irqrestore(&tbl->it_lock, flags);
return 0;
}

--
1.5.2