I'm skeptical since the small code fragment around there has been
ralatively stable for long time.  According to the figures you
posted a while ago, NetBSD/pmax kernel consumes CPU time much more
than it used to be.  The CPU time consumption was increased by
codes which has been added or structural changes in NetBSD kernel.
So, it'd rather better to pursue them than optimizing microtime()
or memcpy() themselves.

> -       *tvp = time;
> -#if (DEC_3MIN + DEC_MAXINE + DEC_3MAXPLUS) > 0
> +       tvp->tv_sec  = time.tv_sec;
> +       tvp->tv_usec = time.tv_usec;
> +
> +#if defined(DEC_MAXINE) || defined(DEC_3MAXPLUS) || \
> +    ( defined(DEC_3MIN) && defined(MIPS3) )
>        tvp->tv_usec += (*platform.clkread)();
>  #endif
> +
>        if (tvp->tv_usec >= 1000000) {

-nisimura