Memory benchmark

[VladoLavor]

I have added a simple API memory benchmark/test.

Example output:

Running GoVPP API calls memory test
For 100000 show-version calls:
		Measured	Threshold
-----------------------------------------
Total alloc:	424.57 MB	250.00 MB
Memory Freed:	5.22 MB 
Heap alloc:	1.92 MB 	5.00 MB 
Objects alloc:	5,499,561
Obj freed:	5,476,772
Objects remain:	22,789		50,000
Message rate:	11534 m/s
Num goroutines:	8
Duration:	8.669396593s

For 100000 create/delete loopback calls:
		Measured	Threshold
-----------------------------------------
Total alloc:	284.17 MB	350.00 MB
Memory Freed:	3.89 MB 
Heap alloc:	2.18 MB 	5.00 MB 
Objects alloc:	4,108,089
Obj freed:	4,079,319
Objects remain:	28,770		50,000
Message rate:	9863 m/s
Num goroutines:	8
Duration:	10.138160233s

It measures 1k, 10k, 100k, and 1M APIs by default. A custom number of APIs can be tested with the -api-num parameter. Thresholds are pre-defined only for default values. The test runs the GetVersion API, which can be called indefinitely.

Signed-off-by: Vladimir Lavor vlavor@cisco.com

[kerart]

LGTM, just some suggestions here and there

[sknat]

Thank you for the PR @VladoLavor ! I made a few comments inline.

[kerart]

Thanks for the update. I added a suggestion to make it easier to add new metrics

[kerart]

Thanks for the update. LGTM

[sknat]

lgtm, thanks !