uvm_loadav: don't recompute schedstate_percpu.spc_nrun

[Scott Cheloha]

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.

ok?

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 29 Jul 2023 00:31:19 -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;
        }
 }