[3.7] [3.8] bpo-36670, regrtest: Fix WindowsLoadTracker() for partial line (GH-16550) (GH-16560)

[miss-islington]

• bpo-36670, regrtest: Fix WindowsLoadTracker() for partial line (bpo-36670, regrtest: Fix WindowsLoadTracker() for partial line #16550)

WindowsLoadTracker.read_output() now uses a short buffer for
incomplete line.

(cherry picked from commit 3e04cd2)

• bpo-36670: Enhance regrtest WindowsLoadTracker (bpo-36670: Enhance regrtest WindowsLoadTracker #16553)

The last line is now passed to the parser even if it does not end
with a newline, but only if it's a valid value.

(cherry picked from commit c65119d)

• bpo-36670: Enhance regrtest (bpo-36670: regrtest WindowsLoadTracker computes LOAD_FACTOR_1 #16556)

• Add log() method: add timestamp and load average prefixes
  to main messages.

• WindowsLoadTracker:

  • LOAD_FACTOR_1 is now computed using SAMPLING_INTERVAL
  • Initialize the load to the arithmetic mean of the first 5 values
    of the Processor Queue Length value (so over 5 seconds), rather
    than 0.0.
  • Handle BrokenPipeError and when typeperf exit.

• format_duration(1.5) now returns '1.5 sec', rather than
  '1 sec 500 ms'

(cherry picked from commit 098e256)
(cherry picked from commit de3195c)

Co-authored-by: Victor Stinner vstinner@python.org

[vstinner]

LGTM, good bot.

[miss-islington]

@vstinner: Status check is done, and it's a success ✅ .

[miss-islington]

@vstinner: Status check is done, and it's a success ✅ .