x/tools/internal/imports: test frequently times out on `dragonfly-amd64` builder

[bcmills]

The test for golang.org/x/tools/internal/imports seems to be timing out on around 25% of runs on the dragonfly-amd64 builder.

Example logs:

• https://build.golang.org/log/e697ac9c8ea86c4aa83321b80d9c1371c7c630fb
• https://build.golang.org/log/7a7c78010de15f81e9b3411c020e1048006e39e2
• https://build.golang.org/log/606423ffa1cb92cf42e35073469762d25b9e282c
• https://build.golang.org/log/ed9923ceaf868e900d12bf6e7c296d916c7f6a2c

The dragonfly-amd64 builder seems to be a bit underpowered in general (see also #29583 and #25796). Perhaps we should set GO_TEST_TIMEOUT_SCALE=2 in its environment and see if that improves the situation for x/tools?

CC @matloob @ianthehat @tdfbsd

[timdarbydotnet]

The builder is on a dedicated machine with a Core I5-6600 cpu and 16GB RAM.

[bcmills]

Hrm. That seems like it should be a good enough machine to run those tests without timing out.

All of the timeouts seem to involve either filesystem operations or go command invocations (which themselves involve many filesystem operations). Is it possible that the builder has high disk contention?

[timdarbydotnet]

The other processes on this machine are very light duty. The only thing that could cause serious filesystem contention is the nightly hammer cleanup process that typically runs around 10am UTC.

These failures feel "racy" to me, in part because they aren't consistent. DragonFly has gone to great lengths in the past year to improve SMP performance and I'm wondering if maybe they removed one lock too many. I have no clue how to troubleshoot that.

[dmitshur]

Dragonfly isn't one of the first-class ports according to the checkbox on https://build.golang.org. It seems no one is actively working on this. As a result, I don't think it's appropriate for this issue to have the Soon label, which is meant for regressions, serious bugs, and outages.

This issue still needs to be investigated and resolved if possible, but unless I'm missing something, it doesn't meet the bar for Soon.

[timdarbydotnet]

cc'ing @tuxillo. Please remove me from the issue as I'm no longer maintaining the DragonFly builder.

[tuxillo]

There have been some changes to master (or tip as you call it I think) branch in DragonFly which might help this issue. I am not sure if they'll be merged to the soon to be released 5.8 RELEASE, which reminds me at that point we'll have to ask you guys to change the 5_6 builder name to 5_8 :)