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>
diff --git a/src/tests/vnet/session/tcp_echo.c b/src/tests/vnet/session/tcp_echo.c
index d76e939..99b6765 100644
--- a/src/tests/vnet/session/tcp_echo.c
+++ b/src/tests/vnet/session/tcp_echo.c
@@ -507,7 +507,7 @@
{
int n_to_read, n_read;
- n_to_read = svm_fifo_max_dequeue (s->rx_fifo);
+ n_to_read = svm_fifo_max_dequeue_cons (s->rx_fifo);
if (!n_to_read)
return;
@@ -1063,7 +1063,7 @@
* message queue */
svm_fifo_unset_event (s->rx_fifo);
- max_dequeue = svm_fifo_max_dequeue (s->rx_fifo);
+ max_dequeue = svm_fifo_max_dequeue_cons (s->rx_fifo);
if (PREDICT_FALSE (!max_dequeue))
return;