IPLD AMT churn benchmarking

[ZenGround0]

The recent discovery of heavy churn in the market actor states AMT has prompted development of a simple tool for benchmarking filecoin amt state. It is in PR here

lotus-bench amt --interval <x> --rounds <y> creates an in memory AMT and runs update operations on a subset of its intervals, printing out a summary. For example if we run lotus-bench amt --interval 4100 --rounds 1 we get as output:

Populating AMT
Measuring AMT

------------
Link Count: 634922
Value Count: 40000000
9923 link nodes 27430652 bytes
625000 value nodes 527993648 bytes
Total bytes: 555424300
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Overwrite 1 out of 4100 values for 1 rounds
round: 0
Measuring 1 rounds of churn

------------
Link Count: 634346
Value Count: 624448
9914 link nodes 27405767 bytes
9757 value nodes 8242529 bytes
Total bytes: 35648296
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This information was useful for me to understand churn properties of the market actor state. Perhaps it will be useful for others.