Break up monolithic iommu table/lock into finer graularity pools and lock
Investigation of multithreaded iperf experiments on an ethernet
interface show the iommu->lock as the hottest lock identified by
lockstat, with something of the order of 21M contentions out of
27M acquisitions, and an average wait time of 26 us for the lock.
This is not efficient. A more scalable design is to follow the ppc
model, where the iommu_map_table has multiple pools, each stretching
over a segment of the map, and with a separate lock for each pool.
This model allows for better parallelization of the iommu map search.
This patch adds the iommu range alloc/free function infrastructure.
Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/iommu-common.h b/include/linux/iommu-common.h
new file mode 100644
index 0000000..bbced83
--- /dev/null
+++ b/include/linux/iommu-common.h
@@ -0,0 +1,51 @@
+#ifndef _LINUX_IOMMU_COMMON_H
+#define _LINUX_IOMMU_COMMON_H
+
+#include <linux/spinlock_types.h>
+#include <linux/device.h>
+#include <asm/page.h>
+
+#define IOMMU_POOL_HASHBITS 4
+#define IOMMU_NR_POOLS (1 << IOMMU_POOL_HASHBITS)
+
+struct iommu_pool {
+ unsigned long start;
+ unsigned long end;
+ unsigned long hint;
+ spinlock_t lock;
+};
+
+struct iommu_map_table {
+ unsigned long table_map_base;
+ unsigned long table_shift;
+ unsigned long nr_pools;
+ void (*lazy_flush)(struct iommu_map_table *);
+ unsigned long poolsize;
+ struct iommu_pool pools[IOMMU_NR_POOLS];
+ u32 flags;
+#define IOMMU_HAS_LARGE_POOL 0x00000001
+#define IOMMU_NO_SPAN_BOUND 0x00000002
+#define IOMMU_NEED_FLUSH 0x00000004
+ struct iommu_pool large_pool;
+ unsigned long *map;
+};
+
+extern void iommu_tbl_pool_init(struct iommu_map_table *iommu,
+ unsigned long num_entries,
+ u32 table_shift,
+ void (*lazy_flush)(struct iommu_map_table *),
+ bool large_pool, u32 npools,
+ bool skip_span_boundary_check);
+
+extern unsigned long iommu_tbl_range_alloc(struct device *dev,
+ struct iommu_map_table *iommu,
+ unsigned long npages,
+ unsigned long *handle,
+ unsigned long mask,
+ unsigned int align_order);
+
+extern void iommu_tbl_range_free(struct iommu_map_table *iommu,
+ u64 dma_addr, unsigned long npages,
+ unsigned long entry);
+
+#endif