Anthony Harivel, Mar 16, 2023 at 16:14: > Sleep for an incremental amount of time if the fwd engine has processed > less than at least half a burst of packets (i.e 16pkts with default > setting) on a polling iteration of testpmd. > > Upon detecting the threshold of >= 16 pkts on an Rxq, reset the sleep > time to zero (i.e. no sleep). > > Sleep time will be increased on each iteration where the low load > conditions remain up to a total of the max sleep time which is set by > the user with the "--max-sleep-us NUM" command line argument or when in > interactive "mode set max_sleep NUM". > > The default max_sleep value is 0, which means that no sleeps will occur > and the default behaviour is unchanged from previously. > > Testing has been performed on AMD EPYC 7702 server with --nb-cores 12. > The results were obtained via turbostat for each individual lcore: > > max_sleep 0 ====== ======== ======== ======== > idle 4Mpps 16Mpps Bursts > =============== ====== ======== ======== ======== > C1-state % 0 0 0 0 > C2-state % 0 0 0 0 > % usage 100 100 100 100 > Watt / core 1.14 1.18 1.19 1.14 > =============== ====== ======== ======== ======== > > max_sleep 500 ====== ======== ======== ======== > idle 4Mpps 16Mpps Bursts > =============== ====== ======== ======== ======== > C1-state % 99 85 74 98.6 > C2-state % 0 0 0 0 > % usage 1 15 26 1 > Watt / core 0.04 0.18 0.28 0 04 > =============== ====== ======== ======== ======== > > max_sleep 1000 ====== ======== ======== ======== > idle 4Mpps 16Mpps Bursts > =============== ====== ======== ======== ======== > C1-state % 0 85 74 0.3 > C2-state % 99 0 0 97.6 > % usage 1 15 25 1 > Watt / core 0.02 0.18 0.28 0 02 > =============== ====== ======== ======== ======== > > On most cases, the consumption of the cores is greatly improved while > still performing zero packet loss. > > Latency test has been performed on each tests above. The CPU has a C1 > latency of 1us and a C2 latency of 400us. On the worst case scenario, Tx > Burst of thousands packets every seconds, the following latency in us > (micro seconds) has been observed: > > =========== ==== ===== ====== > max_sleep 0 500 1000 > ----------- ---- ----- ------ > max latency 14 560 1260 > min latency 5 5 6 > Avg latency 7 305 617 > =========== ==== ===== ====== > > link: > https://www.github.com/torvalds/linux/tree/master/tools/power/x86/turbostat > Signed-off-by: Anthony Harivel <ahari...@redhat.com>
Given the amount of time testpmd is used in local development and automated testing, adding such an option is a great addition to save CPU power. Thanks Anthony. Reviewed-by: Robin Jarry <rja...@redhat.com>
