> Date: Sun, 18 Jun 2023 12:27:17 -0500
> From: Scott Cheloha <[email protected]>
>
> The intent here is to update the load averages every five seconds.
> However:
>
> 1. Measuring elapsed time with the UTC clock is unreliable because of
> settimeofday(2).
>
> 2. "Call uvm_loadav() no more than once every five seconds", is not
> equivalent to "call uvm_loadav() if the current second is equal
> to zero, modulo five".
>
> Not hard to imagine edge cases where timeouts are delayed and
> the load averages are not updated.
>
> So, (1) use the monotonic clock, and (2) keep the next uvm_loadav()
> call time in a static value.
>
> ok?
I really don't see why the calculatin of something vague like the load
average warrants complicating the code like this.
> Index: uvm_meter.c
> ===================================================================
> RCS file: /cvs/src/sys/uvm/uvm_meter.c,v
> retrieving revision 1.42
> diff -u -p -r1.42 uvm_meter.c
> --- uvm_meter.c 28 Dec 2020 14:01:23 -0000 1.42
> +++ uvm_meter.c 18 Jun 2023 17:11:09 -0000
> @@ -87,8 +87,16 @@ void uvmexp_read(struct uvmexp *);
> void
> uvm_meter(void)
> {
> - if ((gettime() % 5) == 0)
> + static time_t next_uvm_loadav;
> + time_t intvl_count, now;
> +
> + now = getuptime();
> + if (now >= next_uvm_loadav) {
> + intvl_count = (now - next_uvm_loadav) / 5 + 1;
> + next_uvm_loadav += 5 * intvl_count;
> uvm_loadav(&averunnable);
> + }
> +
> if (proc0.p_slptime > (maxslp / 2))
> wakeup(&proc0);
> }
>
>
