With IOVA allocation suitably tidied up, we are finally free to opt in
to the per-CPU caching mechanism. The caching alone can provide a modest
improvement over walking the rbtree for weedier systems (iperf3 shows
~10% more ethernet throughput on an ARM Juno r1 constrained to a single
650MHz Cortex-A53), but the real gain will be in sidestepping the rbtree
lock contention which larger ARM-based systems with lots of parallel I/O
are starting to feel the pain of.
Signed-off-by: Robin Murphy <robin.mur...@arm.com>
---
drivers/iommu/dma-iommu.c | 39 ++++++++++++++++++---------------------
1 file changed, 18 insertions(+), 21 deletions(-)
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index c03e2eb4ebbb..292008de68f0 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -282,8 +282,7 @@ static dma_addr_t iommu_dma_alloc_iova(struct iommu_domain
*domain,
{
struct iommu_dma_cookie *cookie = domain->iova_cookie;
struct iova_domain *iovad = &cookie->iovad;
- unsigned long shift, iova_len;
- struct iova *iova = NULL;
+ unsigned long shift, iova_len, iova = 0;
if (cookie->type == IOMMU_DMA_MSI_COOKIE) {
cookie->msi_iova += size;
@@ -292,41 +291,39 @@ static dma_addr_t iommu_dma_alloc_iova(struct
iommu_domain *domain,
shift = iova_shift(iovad);
iova_len = size >> shift;
+ /*
+ * Freeing non-power-of-two-sized allocations back into the IOVA caches
+ * will come back to bite us badly, so we have to waste a bit of space
+ * rounding up anything cacheable to make sure that can't happen. The
+ * order of the unadjusted size will still match upon freeing.
+ */
+ if (iova_len < (1 << (IOVA_RANGE_CACHE_MAX_SIZE - 1)))
+ iova_len = roundup_pow_of_two(iova_len);
if (domain->geometry.force_aperture)
dma_limit = min(dma_limit, domain->geometry.aperture_end);
/* Try to get PCI devices a SAC address */
if (dma_limit > DMA_BIT_MASK(32) && dev_is_pci(dev))
- iova = alloc_iova(iovad, iova_len, DMA_BIT_MASK(32) >> shift,
- true);
- /*
- * Enforce size-alignment to be safe - there could perhaps be an
- * attribute to control this per-device, or at least per-domain...
- */
- if (!iova)
- iova = alloc_iova(iovad, iova_len, dma_limit >> shift, true);
+ iova = alloc_iova_fast(iovad, iova_len, DMA_BIT_MASK(32) >>
shift);
- return (dma_addr_t)iova->pfn_lo << shift;
+ if (!iova)
+ iova = alloc_iova_fast(iovad, iova_len, dma_limit >> shift);
+
+ return (dma_addr_t)iova << shift;
}
static void iommu_dma_free_iova(struct iommu_dma_cookie *cookie,
dma_addr_t iova, size_t size)
{
struct iova_domain *iovad = &cookie->iovad;
- struct iova *iova_rbnode;
+ unsigned long shift = iova_shift(iovad);
/* The MSI case is only ever cleaning up its most recent allocation */
- if (cookie->type == IOMMU_DMA_MSI_COOKIE) {
+ if (cookie->type == IOMMU_DMA_MSI_COOKIE)
cookie->msi_iova -= size;
- return;
- }
-
- iova_rbnode = find_iova(iovad, iova_pfn(iovad, iova));
- if (WARN_ON(!iova_rbnode))
- return;
-
- __free_iova(iovad, iova_rbnode);
+ else
+ free_iova_fast(iovad, iova >> shift, size >> shift);
}
static void __iommu_dma_unmap(struct iommu_domain *domain, dma_addr_t dma_addr,
--
2.11.0.dirty
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