[flex counter] Flex counter threads consume too much CPU resources.

[StormLiangMS]

Description

syncd will start multi threads to collect counters, which occupies lots of CPU resources in some platform, how bad it could be? It depends on the quantity of ports and queues, and the CPU.

Steps to reproduce the issue:

1. To enable the flex counter
2. To check the CPU usage by top command.

Describe the results you received:

Describe the results you expected:

Output of show version:

SONiC Software Version: SONiC.20201231.41
Distribution: Debian 10.11
Kernel: 4.19.0-12-2-amd64
Build commit: 84eefd6578
Build date: Sat Oct 30 12:01:42 UTC 2021
Built by: cloudtest@3cfd51cec000000

Platform: x86_64-arista_7260cx3_64
HwSKU: Arista-7260CX3-D108C8
ASIC: broadcom
ASIC Count: 1
Serial Number: JPE20222159
Uptime: 02:03:32 up 10:09,  1 user,  load average: 1.54, 1.78, 1.87

Output of show techsupport:

(paste your output here or download and attach the file here )

Additional information you deem important (e.g. issue happens only occasionally):