From: "Bruce Richardson" <bruce.richard...@intel.com>
Add in some additional comments around more complex areas of the code
so as to make the code easier to read and understand.
Signed-off-by: Bruce Richardson <bruce.richardson at intel.com>
---
lib/librte_distributor/rte_distributor.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/lib/librte_distributor/rte_distributor.c
b/lib/librte_distributor/rte_distributor.c
index 585ff88..656ee5c 100644
--- a/lib/librte_distributor/rte_distributor.c
+++ b/lib/librte_distributor/rte_distributor.c
@@ -92,6 +92,7 @@ struct rte_distributor {
unsigned num_workers; /**< Number of workers polling */
uint32_t in_flight_tags[RTE_MAX_LCORE];
+ /**< Tracks the tag being processed per core, 0 == no pkt */
struct rte_distributor_backlog backlog[RTE_MAX_LCORE];
union rte_distributor_buffer bufs[RTE_MAX_LCORE];
@@ -282,10 +283,22 @@ rte_distributor_process(struct rte_distributor *d,
next_mb = mbufs[next_idx++];
next_value = (((int64_t)(uintptr_t)next_mb)
<< RTE_DISTRIB_FLAG_BITS);
+ /*
+ * Set the low bit on the tag, so we can guarantee that
+ * we never store a tag value of zero. That means we can
+ * use the zero-value to indicate that no packet is
+ * being processed by a worker.
+ */
new_tag = (next_mb->hash.rss | 1);
uint32_t match = 0;
unsigned i;
+ /*
+ * to scan for a match use "xor" and "not" to get a 0/1
+ * value, then use shifting to merge to single "match"
+ * variable, where a one-bit indicates a match for the
+ * worker given by the bit-position
+ */
for (i = 0; i < d->num_workers; i++)
match |= (!(d->in_flight_tags[i] ^ new_tag)
<< i);
--
2.1.1
