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authorMartin Svec <martin.svec@zoner.cz>2013-01-15 12:43:35 -0800
committerNicholas Bellinger <nab@linux-iscsi.org>2013-02-13 11:27:31 -0800
commit8f67835f1e389978bb0809d5e528961986aa2a69 (patch)
tree4bee48a706dec1da02e927309b6851f57730337c /drivers/target/target_core_rd.c
parentd09816ae8fc05322b4e37a589537b4ecdca28a0d (diff)
target/rd: improve sg_table lookup scalability
Sequential scan of rd_dev->sg_table_array in rd_get_sg_table is a serious I/O performance bottleneck for large rd LUNs. Fix this by computing the sg_table index directly from page offset because all sg_tables (except the last one) have the same number of pages. Tested with 90 GiB rd_mcp LUN, where the patch improved maximal random R/W IOPS by more than 100-150%, depending on actual hardware and SAN setup. Signed-off-by: Martin Svec<martin.svec@zoner.cz> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Diffstat (limited to 'drivers/target/target_core_rd.c')
-rw-r--r--drivers/target/target_core_rd.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/drivers/target/target_core_rd.c b/drivers/target/target_core_rd.c
index 0457de362e6..b0fff52c990 100644
--- a/drivers/target/target_core_rd.c
+++ b/drivers/target/target_core_rd.c
@@ -256,10 +256,12 @@ static void rd_free_device(struct se_device *dev)
static struct rd_dev_sg_table *rd_get_sg_table(struct rd_dev *rd_dev, u32 page)
{
- u32 i;
struct rd_dev_sg_table *sg_table;
+ u32 i, sg_per_table = (RD_MAX_ALLOCATION_SIZE /
+ sizeof(struct scatterlist));
- for (i = 0; i < rd_dev->sg_table_count; i++) {
+ i = page / sg_per_table;
+ if (i < rd_dev->sg_table_count) {
sg_table = &rd_dev->sg_table_array[i];
if ((sg_table->page_start_offset <= page) &&
(sg_table->page_end_offset >= page))