On 2025-07-07 11:00, Naga Harish K, S V wrote:
-----Original Message-----
From: Mattias Rönnblom <hof...@lysator.liu.se>
Sent: Thursday, July 3, 2025 1:50 AM
To: Naga Harish K, S V <s.v.naga.haris...@intel.com>; Mattias Rönnblom
<mattias.ronnb...@ericsson.com>; dev@dpdk.org
Cc: Jerin Jacob <jer...@marvell.com>; Peter Nilsson
<peter.j.nils...@ericsson.com>
Subject: Re: [PATCH] event/eth_tx: prefetch mbuf headers
On 2025-05-27 12:55, Naga Harish K, S V wrote:
-----Original Message-----
From: Mattias Rönnblom <mattias.ronnb...@ericsson.com>
Sent: Friday, March 28, 2025 11:14 AM
To: dev@dpdk.org
Cc: Mattias Rönnblom <hof...@lysator.liu.se>; Naga Harish K, S V
<s.v.naga.haris...@intel.com>; Jerin Jacob <jer...@marvell.com>;
Mattias Rönnblom <mattias.ronnb...@ericsson.com>; Peter Nilsson
<peter.j.nils...@ericsson.com>
Subject: [PATCH] event/eth_tx: prefetch mbuf headers
Prefetch mbuf headers, resulting in ~10% throughput improvement when
the Ethernet RX and TX Adapters are hosted on the same core (likely
~2x in case a dedicated TX core is used).
Signed-off-by: Mattias Rönnblom <mattias.ronnb...@ericsson.com>
Tested-by: Peter Nilsson <peter.j.nils...@ericsson.com>
---
lib/eventdev/rte_event_eth_tx_adapter.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/lib/eventdev/rte_event_eth_tx_adapter.c
b/lib/eventdev/rte_event_eth_tx_adapter.c
index 67fff8b7d6..d740ae00f9 100644
--- a/lib/eventdev/rte_event_eth_tx_adapter.c
+++ b/lib/eventdev/rte_event_eth_tx_adapter.c
@@ -598,6 +598,12 @@ txa_process_event_vector(struct
txa_service_data
*txa,
return nb_tx;
}
+static inline void
+txa_prefetch_mbuf(struct rte_mbuf *mbuf) {
+ rte_mbuf_prefetch_part1(mbuf);
+}
+
static void
txa_service_tx(struct txa_service_data *txa, struct rte_event *ev,
uint32_t n)
@@ -608,6 +614,20 @@ txa_service_tx(struct txa_service_data *txa,
struct rte_event *ev,
stats = &txa->stats;
+ for (i = 0; i < n; i++) {
+ struct rte_event *event = &ev[i];
+
+ if (unlikely(event->event_type & RTE_EVENT_TYPE_VECTOR))
This gives a branch prediction advantage to non-vector events. Is that the
intention?
Yes.
I think all event-types need to be equally weighted. My ask was to remove the
"unlikely" for vector events.
This is not possible. One branch will always be cheaper. If you leave
out unlikely()/likely(), you leave all control to compiler heuristics.
In this case, I think the resulting object code will be identical (on GCC).
RTE_EVENT_TYPE_VECTOR will result in fewer events, and thus the
per-event overhead is less of an issue. So if you weigh the importance
of vector and non-vector use cases equally, you should optimize for the
non-vector case.
{
+ struct rte_event_vector *vec = event->vec;
+ struct rte_mbuf **mbufs = vec->mbufs;
+ uint32_t k;
+
+ for (k = 0; k < vec->nb_elem; k++)
+ txa_prefetch_mbuf(mbufs[k]);
+ } else
+ txa_prefetch_mbuf(event->mbuf);
+ }
+
nb_tx = 0;
for (i = 0; i < n; i++) {
uint16_t port;
--
2.43.0
