session: fix prefetch out of struct bound on Arm

CLIB_PREFETCH (s->tx_fifo, 2 * CLIB_CACHE_LINE_BYTES, LOAD);
sizeof(svm_fifo_t) is 128 bytes

Note on 64B cacheline size Arm machine,
CLIB_CACHE_LINE_BYTES 128
CLIB_CACHE_PREFETCH_BYTES 6

above CLIB_PREFETCH () macro will be expand to
__builtin_prefetch(s->tx_fifo)
__builtin_prefetch(s->tx_fifo + 64)
__builtin_prefetch(s->tx_fifo + 128) << prefetch out of range
__builtin_prefetch(s->tx_fifo + 192) << the same here

Solution:
Change to CLIB_PREFETCH (s->tx_fifo, sizeof (*(s->tx_fifo)), LOAD);

Type: fix
Signed-off-by: Tianyu Li <tianyu.li@arm.com>
Reviewed-by: Lijian Zhang <lijian.zhang@arm.com>
Change-Id: I745cbce3dbe5afcab53c39189d18392f569df5aa

diff --git a/src/vnet/session/session_node.c b/src/vnet/session/session_node.c
index 969f88c..18fb61d 100644 (file)
--- a/src/vnet/session/session_node.c
+++ b/src/vnet/session/session_node.c
@@ -1580,7 +1580,7 @@ session_event_dispatch_io (session_worker_t * wrk, vlib_node_runtime_t * node,
       s = session_event_get_session (wrk, e);
       if (PREDICT_FALSE (!s))
        break;
-      CLIB_PREFETCH (s->tx_fifo, 2 * CLIB_CACHE_LINE_BYTES, LOAD);
+      CLIB_PREFETCH (s->tx_fifo, sizeof (*(s->tx_fifo)), LOAD);
       wrk->ctx.s = s;
       /* Spray packets in per session type frames, since they go to
        * different nodes */