4d7bf41beb
TestExec and TestExecHelper check for a workaround of a particular OS bug on darwin that's triggered more often via asynchronous preemption. As part of this, the test sets up 100 CPU-bound goroutines, and sets GOMAXPROCS to 50, sleeping for a little bit before calling Exec. Thus far, this is fine because the scheduler runs the Execing goroutine in a timely manner. However, CL 309869 will reduce the minimum heap size, causing a GC to happen during the test. On a 16 CPU machine, with GOMAXPROCS at 50, and 100 CPU-bound goroutines, both the OS scheduler and the Go scheduler are severly oversaturated. As a result, the test often (not always, but often) runs out for the full lifetime of those 100 goroutines, which run for about 1 second. The minimum heap size reduction is not necessary to trigger this; an additional call to runtime.GC in the helper is also sufficient to trigger this delay. The delay on its own isn't great, since it adds a whole second to all.bash on its own. However, it also seems correlated with other subprocess tests in the syscall package, namely TestPassFD and TestFcntlFlock. These tests fail in a fairly superficial way: the file descriptor for the temporary directories they make gets clobbered, is closed, or becomes stale. Change-Id: I213dd5e38967d19a8b317e6d4c5024b57f9e3fed Reviewed-on: https://go-review.googlesource.com/c/go/+/360574 Trust: Michael Knyszek <mknyszek@google.com> Run-TryBot: Michael Knyszek <mknyszek@google.com> Reviewed-by: Ian Lance Taylor <iant@golang.org> |
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