adding memory and disk usage stats to bench tests

[MarkWolters]

This PR adds new columns to the BenchYAML tests measuring memory and disk usage. The output looks as follows:

Configuration:
  efConstruction        : 100
  addHierarchy          : true
  neighborOverflow      : 1.2
  usePruning            : true
  M                     : 32

Overquery    Avg QPS (of 3)    ± Std Dev    CV %        Mean Latency (ms)    Avg Visited    Recall@10    Max heap usage    Max offheap usage    Total file size    Number of files    Index build time   
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1.00         45799.0           706.6        1.5         0.192                349.6          0.75         1127.6            116.5                116.5              1                  38.72              
2.00         38702.6           344.8        0.9         0.237                507.2          0.89         494.1             116.5                116.5              1                  38.72              
5.00         25087.6           463.2        1.8         0.363                922.1          0.95         795.4             116.5                116.5              1                  38.72              
10.00        16557.8           45.5         0.3         0.551                1512.0         0.97         1219.3            116.5                116.5              1                  38.72         

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[jshook]

Perhaps clarify the unit here, such as getIndexBuildTimeMillis or getIndexBuildTimeSeconds

[MarkWolters]

good point, I will add that.

[jshook]

Does import not work for this symbol?

[MarkWolters]

I do not recall why this is fully qualified but I will clean it up

[jshook]

Just an idea for an improvement, DiagnosticLevel could control both snapshot collection and then iterate through the snapshots, even if there are zero. Just a simplification possibly.

[MarkWolters]

good idea, will look into it

[jshook]

I would strongly suggest using the notify mechanism that allows you to see update events within the filesystem, to avoid traversing things fully every time you want a read. Then you could easily keep a current view that only processes deltas for changes as they occur. This would possibly move some FS IO out of the measured bucket so that IO measurements are less perturbed by infra code.

[MarkWolters]

Thank you, this is great feedback. I'll hold off on this PR until I get that in place

[jshook]

I've approved this, but please see my comments regarding notify. I think you might have a better way to implement this which is well supported and much more efficient.