I ran cmd/compile with the block profiler enabled (see CL 39208), and examined the results with pprof. The header in the pdf says: "Showing nodes accounting for 28.16mins, 99.72% of 28.24mins total". And the biggest node in the pdf showed: "28.16mins (99.72%)". But the total compilation tool less than 5 seconds of real time. Unless I'm holding it wrong, it appears that there's a unit error somewhere in block profiling / pprof.