Yes, good point, I neglected strace startup overhead, though it still seems to slow down the program by a factor of 5 compared to perf trace (2 ms vs. 0.4 ms on my machine). Indeed mitigations probably hurt here. Also fun, try time strace strace -tt ./prog to watch the walltime explode.

I guess glibc's inability to be truly static must make the biggest difference. Compiling my program with -static, I get a 2-3x speedup, but even still, callgrind suggests half of the time is spent in _dl_relocate_object, since I guess even staticly-linked glibc needs to dlopen some things, which probably your minimal libc doesn't require at all :).