Turn off Background fetcher in Soci Config

[sbuckfelder]

Investigate the impact of turning off the prefetcher.

[vkuzniet]

Turning off background fetch does not seem to improve things. The results with and without background fetch seem to be within the same range.
Below are the results for a few runs to showcase the facts.

Getting to ready line for drupal with background fetch enabled:

{
  "testName": "SociRundrupal",
  "numberOfTests": 10,
  "testTimes": [
    3.514366104,
    3.438325975,
    3.386830468,
    3.484538835,
    3.5999828799999998,
    3.381849567,
    3.55579802,
    3.487010156,
    3.005520713,
    3.498268507
  ],
  "stdDev": 0.1571243835514334,
  "mean": 3.4352491225,
  "min": 3.005520713,
  "pct25": 3.3843400175,
  "pct50": 3.484538835,
  "pct75": 3.5063173055,
  "pct90": 3.55579802,
  "max": 3.5999828799999998
}

Getting to ready line for drupal with background fetch disabled:

{
  "testName": "SociRundrupal",
  "numberOfTests": 10,
  "testTimes": [
    3.427106556,
    3.736782046,
    3.826452474,
    3.347792385,
    4.078158608,
    3.545986215,
    3.651143014,
    3.406338622,
    3.641549722,
    4.979371583
  ],
  "stdDev": 0.45501353945730844,
  "mean": 3.7640681225000003,
  "min": 3.347792385,
  "pct25": 3.416722589,
  "pct50": 3.641549722,
  "pct75": 3.78161726,
  "pct90": 4.078158608,
  "max": 4.979371583
}

Getting to ready line for jenkins with background fetch enabled:

{
  "testName": "SociRunjenkins",
  "numberOfTests": 10,
  "testTimes": [
    10.054356415,
    9.494009386,
    9.627321754,
    9.66908636,
    11.155647402,
    9.584445945,
    9.279093966,
    9.55490319,
    9.401226454,
    9.587650685
  ],
  "stdDev": 0.5089182780597901,
  "mean": 9.7407741557,
  "min": 9.279093966,
  "pct25": 9.447617919999999,
  "pct50": 9.584445945,
  "pct75": 9.648204057000001,
  "pct90": 10.054356415,
  "max": 11.155647402
}

Getting to ready line for jenkins with background fetch disabled:

{
  "testName": "SociRunjenkins",
  "numberOfTests": 10,
  "testTimes": [
    9.361044952,
    9.750638978,
    9.947722197000001,
    9.234274562,
    9.708358833,
    9.228201503,
    9.054713528,
    9.191678314,
    9.824592823,
    9.515478995
  ],
  "stdDev": 0.2942896685220635,
  "mean": 9.4816704685,
  "min": 9.054713528,
  "pct25": 9.2099399085,
  "pct50": 9.361044952,
  "pct75": 9.7294989055,
  "pct90": 9.824592823,
  "max": 9.947722197000001
}

[vkuzniet]

Large images also do not seem to benefit from disabling the background fetch. Running test with Tensorflow image shows the degradation in getting to ready line with background fetch disabled.

Getting to ready line for Tensorflow image with background fetch enabled:

{
  "testName": "SociRunTensorHelloWorld",
  "numberOfTests": 10,
  "testTimes": [
    19.610846123,
    19.165775153,
    20.629963265,
    20.721168575,
    19.42073217,
    19.330365578,
    19.632302849,
    20.622923324,
    19.807134995,
    20.03266827
  ],
  "stdDev": 0.5481311674358874,
  "mean": 19.8973880302,
  "min": 19.165775153,
  "pct25": 19.375548874,
  "pct50": 19.632302849,
  "pct75": 20.327795797,
  "pct90": 20.629963265,
  "max": 20.721168575
}

Getting to ready line for Tensorflow image with background fetch disabled:

{
  "testName": "SociRunTensorHelloWorld",
  "numberOfTests": 10,
  "testTimes": [
    19.65265909,
    20.893706043,
    21.212172436,
    20.133621139,
    19.299996586,
    19.629116495,
    21.004703673,
    19.637957393,
    19.86712194,
    22.457070123
  ],
  "stdDev": 0.937789828527017,
  "mean": 20.378812491799998,
  "min": 19.299996586,
  "pct25": 19.633536944,
  "pct50": 19.86712194,
  "pct75": 20.949204858,
  "pct90": 21.212172436,
  "max": 22.457070123
}

[vkuzniet]

PR: #176

[vkuzniet]

Document with the results of benchmarking: Performance effects of turning off background fetch.pdf