svm_fifo rework to avoid contention on cursize

Problems Addressed:
- Contention of cursize by producer and consumer.
- Reduce the no of modulo operations.

Changes:
- Synchronization between producer and consumer changed from cursize
  to head and tail indexes
  Implications: reduces the usable size of fifo by 1.
- Using weaker memory ordering C++11 atomics to access head and tail
  based on producer and consumer role.
- Head and tail indexes are unsigned 32 bit integers. Additions and
  subtraction on them are implicit 32 bit Modulo operation.
- Adding weaker memory ordering variants of max_enq, max_deq, is_empty
  and is_full Using them appropriately in all places.

Perfomance improvement (iperf3 via Hoststack):

iperf3 Server: Marvell ThunderX2(AArch64) - iperf3 Client: Skylake(x86)
   ~6%(256 rxd/txd) - ~11%(2048 rxd/txd)

Change-Id: I1d484e000e437430fdd5a819657d1c6b62443018
Signed-off-by: Sirshak Das <sirshak.das@arm.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/vnet/session-apps/proxy.c b/src/vnet/session-apps/proxy.c
index 0d4cdd43c1c..6542c160f63 100644
--- a/src/vnet/session-apps/proxy.c
+++ b/src/vnet/session-apps/proxy.c
@@ -227,7 +227,7 @@ proxy_rx_callback (session_t * s)
       ASSERT (rx_fifo->master_thread_index == thread_index);
       ASSERT (tx_fifo->master_thread_index == thread_index);
 
-      max_dequeue = svm_fifo_max_dequeue (s->rx_fifo);
+      max_dequeue = svm_fifo_max_dequeue_cons (s->rx_fifo);
 
       if (PREDICT_FALSE (max_dequeue == 0))
 	return 0;