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Date:      Mon, 1 Dec 1997 22:17:39 -0500 (EST)
From:      David Petrou <dpetrou@KINCLAITH.PDL.CS.CMU.EDU>
To:        freebsd-stable@freebsd.org
Subject:   RE: CPU Load
Message-ID:  <199712020317.TAA19733@hub.freebsd.org>
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It seems that there's a lot of misinformation being posted here re:
cpu load.  Just look at the relevant code from vm/vm_meter.c:

static void
loadav(struct loadavg *avg)
{
        register int i, nrun;
        register struct proc *p;

        for (nrun = 0, p = allproc.lh_first; p != 0; p = p->p_list.le_next) {
                switch (p->p_stat) {
                case SSLEEP:
                        if (p->p_priority > PZERO || p->p_slptime != 0)
                                continue;
                        /* fall through */
                case SRUN:
                case SIDL:
                        nrun++;
                }
        }
        for (i = 0; i < 3; i++)
                avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
                    nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
}

The important part is nrun...  If a process is in SRUN or SIDL or it
has a higher priority (lower numerically) than PZERO _AND_ it has
slept less than a second, the process is counted.  (That last clause
covers fast disk operations...)

David

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