[dpdk-dev] [PATCH v5 6/6] lib/lpm: data update optimization for v20

[Ruifeng Wang]

The table entries were updated field by field. There were two issues:
1. bitwise operations are read-modify-write sequences and not atomic,
   nor efficient.
2. the above non-atomic operations causes entries out of synchronization
   and inconsistency.
This patch combines the fields into a one-go 32bit entry update to avoid
inconsistency and as a bonus save CPU cycles.

Suggested-by: Gavin Hu <gavin.hu at arm.com>
Signed-off-by: Ruifeng Wang <ruifeng.wang at arm.com>
Reviewed-by: Gavin Hu <gavin.hu at arm.com>
---
 lib/librte_lpm/rte_lpm.c | 35 +++++++++++++++++++++++++----------
 1 file changed, 25 insertions(+), 10 deletions(-)

diff --git a/lib/librte_lpm/rte_lpm.c b/lib/librte_lpm/rte_lpm.c
index d86248713..95e2f75aa 100644
--- a/lib/librte_lpm/rte_lpm.c
+++ b/lib/librte_lpm/rte_lpm.c
@@ -906,9 +906,14 @@ add_depth_big_v20(struct rte_lpm_v20 *lpm, uint32_t ip_masked, uint8_t depth,
 
 		/* Set tbl8 entry. */
 		for (i = tbl8_index; i < (tbl8_index + tbl8_range); i++) {
-			lpm->tbl8[i].depth = depth;
-			lpm->tbl8[i].next_hop = next_hop;
-			lpm->tbl8[i].valid = VALID;
+			struct rte_lpm_tbl_entry_v20 new_tbl8_entry = {
+				.valid = VALID,
+				.depth = depth,
+				.valid_group = lpm->tbl8[i].valid_group,
+			};
+			new_tbl8_entry.next_hop = next_hop;
+			__atomic_store(&lpm->tbl8[i], &new_tbl8_entry,
+					__ATOMIC_RELAXED);
 		}
 
 		/*
@@ -943,19 +948,29 @@ add_depth_big_v20(struct rte_lpm_v20 *lpm, uint32_t ip_masked, uint8_t depth,
 
 		/* Populate new tbl8 with tbl24 value. */
 		for (i = tbl8_group_start; i < tbl8_group_end; i++) {
-			lpm->tbl8[i].valid = VALID;
-			lpm->tbl8[i].depth = lpm->tbl24[tbl24_index].depth;
-			lpm->tbl8[i].next_hop =
-					lpm->tbl24[tbl24_index].next_hop;
+			struct rte_lpm_tbl_entry_v20 new_tbl8_entry = {
+				.valid = VALID,
+				.depth = lpm->tbl24[tbl24_index].depth,
+				.valid_group = lpm->tbl8[i].valid_group,
+			};
+			new_tbl8_entry.next_hop =
+				lpm->tbl24[tbl24_index].next_hop;
+			__atomic_store(&lpm->tbl8[i], &new_tbl8_entry,
+					__ATOMIC_RELAXED);
 		}
 
 		tbl8_index = tbl8_group_start + (ip_masked & 0xFF);
 
 		/* Insert new rule into the tbl8 entry. */
 		for (i = tbl8_index; i < tbl8_index + tbl8_range; i++) {
-			lpm->tbl8[i].valid = VALID;
-			lpm->tbl8[i].depth = depth;
-			lpm->tbl8[i].next_hop = next_hop;
+			struct rte_lpm_tbl_entry_v20 new_tbl8_entry = {
+				.valid = VALID,
+				.depth = depth,
+				.valid_group = lpm->tbl8[i].valid_group,
+			};
+			new_tbl8_entry.next_hop = next_hop;
+			__atomic_store(&lpm->tbl8[i], &new_tbl8_entry,
+					__ATOMIC_RELAXED);
 		}
 
 		/*
-- 
2.17.1