…penBSD

Decrease the slop everywhere else, since NetBSD and OpenBSD seem to be
the only ones that miss by that much.

For #50189
Updates #36108

Change-Id: I22ac39cc7c254e40358fcd933b5a6016629602c3
Reviewed-on: https://go-review.googlesource.com/c/go/+/372215
Trust: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

The 'd' constant is intentionally set fairly long to allow for builder
jitter; however, dFromDuration previously hard-coded only 1ms of
downward timing slop.

That slop can be introduced due to time spent between the call to
WaitN in the previous runWait and the call to time.Now in the current
runWait, and empirically may be a bit larger than 1ms on certain
builders (especially the android-amd64-emu builders, which also have
more clock drift than many other platforms; see golang/go#42513).

In addition, on some BSD platforms the slop in the upward direction
may actually be longer than d no matter how generously d is set. That
appears to be a platform bug (see golang/go#50189).

This change adjusts dFromDuration to round to the nearest d instead of
biasing in one direction or the other, and allows an additional factor
of slop on the affected BSD platforms.

Fixes #44067

Change-Id: Id4c073bee545be2291ad98158d764e19db0160cb
Reviewed-on: https://go-review.googlesource.com/c/time/+/383175
Trust: Benny Siegert <bsiegert@gmail.com>
Reviewed-by: Sameer Ajmani <sameer@golang.org>
Trust: Bryan Mills <bcmills@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

This applies the net package CL 365334, CL 366176, CL 372215 to the os
package.

CL 365334:

    These tests were checking for fairly narrow timing windows, but were
    running in parallel and heavily dependent on timer and goroutine
    scheduling. This change eliminates unnecessary goroutines, runs the
    tests sequentially (dramatically shortening the timeouts to reduce the
    penalty of doing so), and uses timestamp comparison instead of
    background timers to hopefully gain some robustness from monotonic
    timestamps.

    Many of the other tests from this package would benefit from similar
    simplifications, which we can apply if and when we notice flaky
    failures or want to improve the latency of running the test.

CL 366176:

    It appears that at least the OpenBSD kernel gets sloppier the longer
    the timeout we give it, up to an observed overhead of around 25%.
    Let's give it a little more than that (33%) in the comparison, and
    also increase the growth curve to match the actual observed times
    instead of exponential initial growth.

CL 372215:

    Decrease the slop everywhere else, since NetBSD and OpenBSD seem to be
    the only ones that miss by that much.

For #36108
For #50189
Fixes #50725 (we hope)

Change-Id: I0854d27af67ca9fcf0f9d9e4ff67acff4c2effc8
Reviewed-on: https://go-review.googlesource.com/c/go/+/415234
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>

This applies the net package CL 365334, CL 366176, CL 372215 to the os
package.

CL 365334:

    These tests were checking for fairly narrow timing windows, but were
    running in parallel and heavily dependent on timer and goroutine
    scheduling. This change eliminates unnecessary goroutines, runs the
    tests sequentially (dramatically shortening the timeouts to reduce the
    penalty of doing so), and uses timestamp comparison instead of
    background timers to hopefully gain some robustness from monotonic
    timestamps.

    Many of the other tests from this package would benefit from similar
    simplifications, which we can apply if and when we notice flaky
    failures or want to improve the latency of running the test.

CL 366176:

    It appears that at least the OpenBSD kernel gets sloppier the longer
    the timeout we give it, up to an observed overhead of around 25%.
    Let's give it a little more than that (33%) in the comparison, and
    also increase the growth curve to match the actual observed times
    instead of exponential initial growth.

CL 372215:

    Decrease the slop everywhere else, since NetBSD and OpenBSD seem to be
    the only ones that miss by that much.

For golang#36108
For golang#50189
Fixes golang#50725 (we hope)

Change-Id: I0854d27af67ca9fcf0f9d9e4ff67acff4c2effc8
Reviewed-on: https://go-review.googlesource.com/c/go/+/415234
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>