@@ -13,6 +13,10 @@ In the sample application a user defined callback is applied to all received
packets to add a timestamp. A separate callback is applied to all packets
prior to transmission to calculate the elapsed time, in CPU cycles.
+If hardware timestamping is supported by the NIC, the sample application will
+also display the average latency since the packet was timestamped in hardware,
+on top of the latency since the packet was received and processed by the RX
+callback.
Compiling the Application
-------------------------
@@ -36,7 +40,10 @@ To run the example in a ``linux`` environment:
.. code-block:: console
- ./build/rxtx_callbacks -l 1 -n 4
+ ./build/rxtx_callbacks -l 1 -n 4 -- [-t]
+
+Use -t to enable hardware timestamping. If not supported by the NIC, an error
+will be displayed.
Refer to *DPDK Getting Started Guide* for general information on running
applications and the Environment Abstraction Layer (EAL) options.
@@ -50,6 +50,9 @@ include $(RTE_SDK)/mk/rte.vars.mk
CFLAGS += $(WERROR_FLAGS)
+# rte_eth_read_clock is experimental
+CFLAGS += -DALLOW_EXPERIMENTAL_API
+
# workaround for a gcc bug with noreturn attribute
# http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12603
ifeq ($(CONFIG_RTE_TOOLCHAIN_GCC),y)
@@ -4,6 +4,7 @@
#include <stdint.h>
#include <inttypes.h>
+#include <getopt.h>
#include <rte_eal.h>
#include <rte_ethdev.h>
#include <rte_cycles.h>
@@ -17,6 +18,9 @@
#define MBUF_CACHE_SIZE 250
#define BURST_SIZE 32
+static const char usage[] =
+ "%s EAL_ARGS -- [-t]\n";
+
static const struct rte_eth_conf port_conf_default = {
.rxmode = {
.max_rx_pkt_len = ETHER_MAX_LEN,
@@ -25,9 +29,14 @@ static const struct rte_eth_conf port_conf_default = {
static struct {
uint64_t total_cycles;
+ uint64_t total_queue_cycles;
uint64_t total_pkts;
} latency_numbers;
+int hw_timestamping;
+
+#define TICKS_PER_CYCLE_SHIFT 16
+static uint64_t ticks_per_cycle_mult;
static uint16_t
add_timestamps(uint16_t port __rte_unused, uint16_t qidx __rte_unused,
@@ -43,22 +52,42 @@ add_timestamps(uint16_t port __rte_unused, uint16_t qidx __rte_unused,
}
static uint16_t
-calc_latency(uint16_t port __rte_unused, uint16_t qidx __rte_unused,
+calc_latency(uint16_t port, uint16_t qidx __rte_unused,
struct rte_mbuf **pkts, uint16_t nb_pkts, void *_ __rte_unused)
{
uint64_t cycles = 0;
+ uint64_t queue_ticks = 0;
uint64_t now = rte_rdtsc();
+ uint64_t ticks;
unsigned i;
- for (i = 0; i < nb_pkts; i++)
+ if (hw_timestamping)
+ rte_eth_read_clock(port, &ticks);
+
+ for (i = 0; i < nb_pkts; i++) {
cycles += now - pkts[i]->udata64;
+ if (hw_timestamping)
+ queue_ticks += ticks - pkts[i]->timestamp;
+ }
+
latency_numbers.total_cycles += cycles;
+ if (hw_timestamping)
+ latency_numbers.total_queue_cycles += (queue_ticks
+ * ticks_per_cycle_mult) >> TICKS_PER_CYCLE_SHIFT;
+
latency_numbers.total_pkts += nb_pkts;
if (latency_numbers.total_pkts > (100 * 1000 * 1000ULL)) {
printf("Latency = %"PRIu64" cycles\n",
latency_numbers.total_cycles / latency_numbers.total_pkts);
- latency_numbers.total_cycles = latency_numbers.total_pkts = 0;
+ if (hw_timestamping) {
+ printf("Latency from HW = %"PRIu64" cycles\n",
+ latency_numbers.total_queue_cycles
+ / latency_numbers.total_pkts);
+ }
+ latency_numbers.total_cycles = 0;
+ latency_numbers.total_queue_cycles = 0;
+ latency_numbers.total_pkts = 0;
}
return nb_pkts;
}
@@ -77,6 +106,7 @@ port_init(uint16_t port, struct rte_mempool *mbuf_pool)
int retval;
uint16_t q;
struct rte_eth_dev_info dev_info;
+ struct rte_eth_rxconf rxconf;
struct rte_eth_txconf txconf;
if (!rte_eth_dev_is_valid_port(port))
@@ -95,9 +125,20 @@ port_init(uint16_t port, struct rte_mempool *mbuf_pool)
if (retval != 0)
return retval;
+ rxconf = dev_info.default_rxconf;
+
+ if (hw_timestamping) {
+ if (!(dev_info.rx_offload_capa & DEV_RX_OFFLOAD_TIMESTAMP)) {
+ printf("\nERROR: Port %u does not support hardware timestamping\n"
+ , port);
+ return -1;
+ }
+ rxconf.offloads |= DEV_RX_OFFLOAD_TIMESTAMP;
+ }
+
for (q = 0; q < rx_rings; q++) {
retval = rte_eth_rx_queue_setup(port, q, nb_rxd,
- rte_eth_dev_socket_id(port), NULL, mbuf_pool);
+ rte_eth_dev_socket_id(port), &rxconf, mbuf_pool);
if (retval < 0)
return retval;
}
@@ -115,6 +156,27 @@ port_init(uint16_t port, struct rte_mempool *mbuf_pool)
if (retval < 0)
return retval;
+ if (hw_timestamping && ticks_per_cycle_mult == 0) {
+ uint64_t cycles_base = rte_rdtsc();
+ uint64_t ticks_base;
+ retval = rte_eth_read_clock(port, &ticks_base);
+ if (retval != 0)
+ return retval;
+ rte_delay_ms(100);
+ uint64_t cycles = rte_rdtsc();
+ uint64_t ticks;
+ rte_eth_read_clock(port, &ticks);
+ uint64_t c_freq = cycles - cycles_base;
+ uint64_t t_freq = ticks - ticks_base;
+ double freq_mult = (double)c_freq / t_freq;
+ printf("TSC Freq ~= %lu\nHW Freq ~= %lu\nRatio : %f\n",
+ c_freq * 10, t_freq * 10, freq_mult);
+ /* TSC will be faster than internal ticks so freq_mult is > 0
+ * We convert the multiplication to an integer shift & mult
+ */
+ ticks_per_cycle_mult = (1 << TICKS_PER_CYCLE_SHIFT) / freq_mult;
+ }
+
struct ether_addr addr;
rte_eth_macaddr_get(port, &addr);
@@ -177,6 +239,11 @@ main(int argc, char *argv[])
struct rte_mempool *mbuf_pool;
uint16_t nb_ports;
uint16_t portid;
+ struct option lgopts[] = {
+ { NULL, 0, 0, 0 }
+ };
+ int opt, option_index;
+
/* init EAL */
int ret = rte_eal_init(argc, argv);
@@ -186,6 +253,18 @@ main(int argc, char *argv[])
argc -= ret;
argv += ret;
+ while ((opt = getopt_long(argc, argv, "t", lgopts, &option_index))
+ != EOF)
+ switch (opt) {
+ case 't':
+ hw_timestamping = 1;
+ break;
+ default:
+ printf(usage, argv[0]);
+ return -1;
+ }
+ optind = 1; /* reset getopt lib */
+
nb_ports = rte_eth_dev_count_avail();
if (nb_ports < 2 || (nb_ports & 1))
rte_exit(EXIT_FAILURE, "Error: number of ports must be even\n");
@@ -6,6 +6,9 @@
# To build this example as a standalone application with an already-installed
# DPDK instance, use 'make'
+#rte_eth_read_clock is experimental
+allow_experimental_apis = true
+
sources = files(
'main.c'
)