Example:
from torch.utils.benchmark import Timer

results = []
for num_threads in [1, 2, 4]:
    timer = Timer(
        stmt="torch.add(x, y, out=out)",
        setup="""
            n = 1024
            x = torch.ones((n, n))
            y = torch.ones((n, 1))
            out = torch.empty((n, n))
        """,
        num_threads=num_threads,
    )
    results.append(timer.blocked_autorange(min_run_time=5))
    print(
        f"{num_threads} thread{'s' if num_threads > 1 else ' ':<4}"
        f"{results[-1].median * 1e6:>4.0f} us   " +
        (f"({results[0].median / results[-1].median:.1f}x)" if num_threads > 1 else '')
    )

1 thread     376 us   
2 threads    189 us   (2.0x)
4 threads     99 us   (3.8x)


Documentation
Tutorial

(Prototype) FX Graph Mode Quantization