tree 8dac21bb90a2525661dced4a33c8cb0b6850a0c6
parent e9c7ba6fdccf64b16fdadd74106175f95454ec4f
author Thomas Wolf <thomas.wolf@paranor.ch> 1597409678 +0200
committer Thomas Wolf <thomas.wolf@paranor.ch> 1598175564 +0200

FS: use binary search to determine filesystem timestamp resolution

Previous code used a minimum granularity of 1 microsecond and would
iterate 233 times on a system where the resolution is 1 second (for
instance, Java 8 on Mac APFS).

New code uses a binary search between the maximum we care about (2
seconds) and zero, with a minimum granularity of also 1 microsecond.
This takes at most 19 iterations (guaranteed). For a file system with 1
second resolution, it takes 4 iterations (1s, 0.5s, 0.8s, 0.9s). With
an up-front check at 1 microsecond and at 1 millisecond this performs
equally well as the old code on file systems with a fine resolution.
(For instance, Java 11 on Mac APFS.)

Also handle obscure cases where the file timestamp implementation may
yield bogus values (as observed on HP NonStop). If such an error case
occurs, log a warning and abort the measurement at the last good value.

Bug: 565707
Change-Id: I82a96729b50c284be7c23fbdf3d0df1bddf60e41
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>