By truncating time.Time to an int64 nanosecond count, we lose the
ability to precisely order timestamps before 1678 or after 2262, but we
gain (linux/amd64, Go 1.17.1):
name old time/op new time/op delta
JobQueuePushPopDone10k-8 2.85ms ± 5% 2.29ms ± 2% -19.80% (p=0.000 n=20+18)
JobQueueBump-8 34.0µs ± 1% 29.8µs ± 1% -12.35% (p=0.000 n=19+19)
name old alloc/op new alloc/op delta
JobQueuePushPopDone10k-8 2.56MB ± 0% 1.76MB ± 0% -31.31% (p=0.000 n=18+13)
name old allocs/op new allocs/op delta
JobQueuePushPopDone10k-8 23.0 ± 0% 23.0 ± 0% ~ (all equal)
Results for BenchmarkJobQueueBump are with the fixed version, which no
longer depends on b.N for the amount of work performed. rand.Rand.Intn
is cheap at ~10ns per iteration.
This adds a new nanoseconds field to the FileInfo, populates it during
scans and sets the non-truncated time in Chtimes calls.
The actual file modification time is defined as modified_s seconds +
modified_ns nanoseconds. It's expected that the modified_ns field is <=
1e9 (that is, all whole seconds should go in the modified_s field) but
not really enforced. Given that it's an int32 the timestamp can be
adjusted += ~2.9 seconds by the modified_ns field...
GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3431
