On 02/08/23(Wed) 14:22, Claudio Jeker wrote:
> On Mon, Jul 31, 2023 at 10:21:11AM -0500, Scott Cheloha wrote:
> > On Fri, Jul 28, 2023 at 07:36:41PM -0500, Scott Cheloha wrote:
> > > claudio@ notes that uvm_loadav() pointlessly walks the allproc list to
> > > recompute schedstate_percpu.spn_nrun for each CPU.
> > >
> > > We can just use the value instead of recomputing it.
> >
> > Whoops, off-by-one. The current load averaging code includes the
> > running thread in the nrun count if it is *not* the idle thread.
>
> Yes, with this the loadavg seems to be consistent and following the number
> of running processes. The code seems to behave like before (with all its
> quirks).
>
> OK claudio@, this is a good first step. Now I think this code should later
> be moved into kern_sched.c or sched_bsd.c and removed from uvm. Not sure why
> the load calculation is part of memory management...
>
> On top of this I wonder about the per-CPU load calculation. In my opinion
> it is wrong to skip the calculation if the CPU is idle. Because of this
> there is no decay for idle CPUs and that feels wrong to me.
> Do we have a userland utility that reports spc_ldavg?
I don't understand why the SCHED_LOCK() is needed. Since I'm really
against adding new uses for it, could you comment on that?
> > Index: uvm_meter.c
> > ===================================================================
> > RCS file: /cvs/src/sys/uvm/uvm_meter.c,v
> > retrieving revision 1.44
> > diff -u -p -r1.44 uvm_meter.c
> > --- uvm_meter.c 21 Jun 2023 21:16:21 -0000 1.44
> > +++ uvm_meter.c 31 Jul 2023 15:20:37 -0000
> > @@ -102,43 +102,29 @@ uvm_loadav(struct loadavg *avg)
> > {
> > CPU_INFO_ITERATOR cii;
> > struct cpu_info *ci;
> > - int i, nrun;
> > - struct proc *p;
> > - int nrun_cpu[MAXCPUS];
> > + struct schedstate_percpu *spc;
> > + u_int i, nrun = 0, nrun_cpu;
> > + int s;
> >
> > - nrun = 0;
> > - memset(nrun_cpu, 0, sizeof(nrun_cpu));
> >
> > - LIST_FOREACH(p, &allproc, p_list) {
> > - switch (p->p_stat) {
> > - case SSTOP:
> > - case SSLEEP:
> > - break;
> > - case SRUN:
> > - case SONPROC:
> > - if (p == p->p_cpu->ci_schedstate.spc_idleproc)
> > - continue;
> > - /* FALLTHROUGH */
> > - case SIDL:
> > - nrun++;
> > - if (p->p_cpu)
> > - nrun_cpu[CPU_INFO_UNIT(p->p_cpu)]++;
> > - }
> > + SCHED_LOCK(s);
> > + CPU_INFO_FOREACH(cii, ci) {
> > + spc = &ci->ci_schedstate;
> > + nrun_cpu = spc->spc_nrun;
> > + if (ci->ci_curproc != spc->spc_idleproc)
> > + nrun_cpu++;
> > + if (nrun_cpu == 0)
> > + continue;
> > + spc->spc_ldavg = (cexp[0] * spc->spc_ldavg +
> > + nrun_cpu * FSCALE *
> > + (FSCALE - cexp[0])) >> FSHIFT;
> > + nrun += nrun_cpu;
> > }
> > + SCHED_UNLOCK(s);
> >
> > for (i = 0; i < 3; i++) {
> > avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
> > nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
> > - }
> > -
> > - CPU_INFO_FOREACH(cii, ci) {
> > - struct schedstate_percpu *spc = &ci->ci_schedstate;
> > -
> > - if (nrun_cpu[CPU_INFO_UNIT(ci)] == 0)
> > - continue;
> > - spc->spc_ldavg = (cexp[0] * spc->spc_ldavg +
> > - nrun_cpu[CPU_INFO_UNIT(ci)] * FSCALE *
> > - (FSCALE - cexp[0])) >> FSHIFT;
> > }
> > }
> >
>
> --
> :wq Claudio
>
