An extra "go build" was happening, for the sake of -tags=testgo,
which would insert some extra behavior into ./internal/work.
Instead, reuse the test binary as cmd/go directly,
by calling the main func when a special env var is set.
We still duplicate the test binary into testBin,
because we need a "go" executable in that directory for $PATH.
Finally, the special behavior is instead inserted via TestMain.
The numbers below represent how long it takes to run zero tests,
measured via:
benchcmd GoTestNothing go test -run=-
That is, the time it takes to run the first test is reduced by half.
Note that these numbers are on a warm build cache,
so if the -tags=testgo build were to be done from scratch,
the speed-up would be significantly more noticeable.
name old time/op new time/op delta
GoTestNothing 830ms ± 2% 380ms ± 7% -54.23% (p=0.008 n=5+5)
name old user-time/op new user-time/op delta
GoTestNothing 1.64s ± 1% 0.82s ± 3% -50.24% (p=0.008 n=5+5)
name old sys-time/op new sys-time/op delta
GoTestNothing 306ms ± 7% 159ms ±28% -48.15% (p=0.008 n=5+5)
name old peak-RSS-bytes new peak-RSS-bytes delta
GoTestNothing 173MB ± 1% 147MB ± 1% -14.96% (p=0.008 n=5+5)
Change-Id: I1f8fc71269a7b45bc5b82b7228e13f56589d44c3
Reviewed-on: https://go-review.googlesource.com/c/go/+/378294
Trust: Daniel Martí <mvdan@mvdan.cc>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Bryan Mills <bcmills@google.com>