LogSummary shows BlockSync speed 0.0 blocks/sec

[dustinxie]

What version of iotex-core image (or code branch) are you using?

latest

What operating system and processor architecture are you using?

macOS

What did you do? If possible, provide a recipe for reproducing the error.

about the new LogSummary feature, run a testnet node, it starts to sync up latest blocks

What did you expect to see?

it should show a stable sync up speed

What did you see instead?

see 0.0 blocks/sec in between normal speed, like below

BlockSync startingHeight: 20691844, tipHeight: 20691995, targetHeight: 20692244, sync in progress at 53.0 blocks/sec
P2P ConnectedPeers: 38
CPU: 2CPUs User: 18.99% System: 5.29% Idle: 53.97% 
Memory: Total: 3.8 GiB Free: 825.4 MiB Used: 883.3 MiB Cached: 2.3 GiB
Disk: Total: 9.5 GiB Free: 1.2 GiB Used: 8.4 GiB

BlockSync startingHeight: 20704847, tipHeight: 20704881, targetHeight: 20705247, sync in progress at 0.0 blocks/sec
P2P ConnectedPeers: 38
CPU: 2CPUs User: 17.92% System: 4.31% Idle: 56.50% 
Memory: Total: 3.8 GiB Free: 444.7 MiB Used: 912.6 MiB Cached: 2.6 GiB
Disk: Total: 9.5 GiB Free: 1.2 GiB Used: 8.4 GiB

BlockSync startingHeight: 20718556, tipHeight: 20718599, targetHeight: 20718956, sync in progress at 0.0 blocks/sec
P2P ConnectedPeers: 38
CPU: 2CPUs User: 20.24% System: 5.16% Idle: 53.43% 
Memory: Total: 3.8 GiB Free: 870.3 MiB Used: 919.0 MiB Cached: 2.2 GiB
Disk: Total: 9.5 GiB Free: 1.2 GiB Used: 8.4 GiB

BlockSync startingHeight: 20731714, tipHeight: 20731869, targetHeight: 20732114, sync in progress at 61.0 blocks/sec
P2P ConnectedPeers: 38
CPU: 2CPUs User: 18.36% System: 4.36% Idle: 56.36% 
Memory: Total: 3.8 GiB Free: 543.4 MiB Used: 936.2 MiB Cached: 2.5 GiB
Disk: Total: 9.5 GiB Free: 1.2 GiB Used: 8.4 GiB