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.
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;
}
}
