[PATCH v2 2/2] swiotlb: checking whether swiotlb buffer is full with io_tlb_used

Dongli Zhang
2018-12-10T00:36:30Z

This patch uses io_tlb_used to help check whether swiotlb buffer is full.
io_tlb_used is no longer used for only debugfs. It is also used to help
optimize swiotlb_tbl_map_single().

Suggested-by: Joe Jin <joe.jin@oracle.com>
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
---
kernel/dma/swiotlb.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 3979c2c..9300341 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -76,12 +76,10 @@ static phys_addr_t io_tlb_start, io_tlb_end;
*/
static unsigned long io_tlb_nslabs;

-#ifdef CONFIG_DEBUG_FS
/*
* The number of used IO TLB block
*/
static unsigned long io_tlb_used;
-#endif

/*
* This is a free list describing the number of free entries available from
@@ -489,6 +487,10 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
* request and allocate a buffer from that IO TLB pool.
*/
spin_lock_irqsave(&io_tlb_lock, flags);
+
+ if (unlikely(nslots > io_tlb_nslabs - io_tlb_used))
+ goto not_found;
+
index = ALIGN(io_tlb_index, stride);
if (index >= io_tlb_nslabs)
index = 0;
@@ -538,9 +540,7 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
dev_warn(hwdev, "swiotlb buffer is full (sz: %zd bytes)\n", size);
return SWIOTLB_MAP_ERROR;
found:
-#ifdef CONFIG_DEBUG_FS
io_tlb_used += nslots;
-#endif
spin_unlock_irqrestore(&io_tlb_lock, flags);

/*
@@ -602,9 +602,7 @@ void swiotlb_tbl_unmap_single(struct device *hwdev, phys_addr_t tlb_addr,
for (i = index - 1; (OFFSET(i, IO_TLB_SEGSIZE) != IO_TLB_SEGSIZE -1) && io_tlb_list[i]; i--)
io_tlb_list[i] = ++count;

-#ifdef CONFIG_DEBUG_FS
io_tlb_used -= nslots;
-#endif
}
spin_unlock_irqrestore(&io_tlb_lock, flags);
}
--
2.7.4