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Index: sys/dev/hwpmc/hwpmc_mod.c
===================================================================
--- sys/dev/hwpmc/hwpmc_mod.c
+++ sys/dev/hwpmc/hwpmc_mod.c
@@ -1282,8 +1282,16 @@
*/
if (PMC_TO_MODE(pm) == PMC_MODE_TS) {
mtx_pool_lock_spin(pmc_mtxpool, pm);
+
+ /*
+ * Use the saved value calculated after the most recent
+ * thread switch out to start this counter. Reset
+ * the saved count in case another thread from this
+ * process switches in before any threads switch out.
+ */
newvalue = PMC_PCPU_SAVED(cpu,ri) =
pp->pp_pmcs[ri].pp_pmcval;
+ pp->pp_pmcs[ri].pp_pmcval = pm->pm_sc.pm_reloadcount;
mtx_pool_unlock_spin(pmc_mtxpool, pm);
} else {
KASSERT(PMC_TO_MODE(pm) == PMC_MODE_TC,
@@ -1416,31 +1424,43 @@
pcd->pcd_read_pmc(cpu, adjri, &newvalue);
- tmp = newvalue - PMC_PCPU_SAVED(cpu,ri);
-
- PMCDBG3(CSW,SWO,1,"cpu=%d ri=%d tmp=%jd", cpu, ri,
- tmp);
-
if (mode == PMC_MODE_TS) {
+ PMCDBG3(CSW,SWO,1,"cpu=%d ri=%d tmp=%jd (samp)",
+ cpu, ri, PMC_PCPU_SAVED(cpu,ri) - newvalue);
/*
* For sampling process-virtual PMCs,
- * we expect the count to be
- * decreasing as the 'value'
- * programmed into the PMC is the
- * number of events to be seen till
- * the next sampling interrupt.
+ * newvalue is the number of events to be seen
+ * until the next sampling interrupt.
+ * We can just add the events left from this
+ * invocation to the counter, then adjust
+ * in case we overflow our range.
+ *
+ * (Recall that we reload the counter every
+ * time we use it.)
*/
- if (tmp < 0)
- tmp += pm->pm_sc.pm_reloadcount;
mtx_pool_lock_spin(pmc_mtxpool, pm);
- pp->pp_pmcs[ri].pp_pmcval -= tmp;
- if ((int64_t) pp->pp_pmcs[ri].pp_pmcval <= 0)
- pp->pp_pmcs[ri].pp_pmcval +=
+
+ pp->pp_pmcs[ri].pp_pmcval += newvalue;
+ if (pp->pp_pmcs[ri].pp_pmcval >
+ pm->pm_sc.pm_reloadcount)
+ pp->pp_pmcs[ri].pp_pmcval -=
pm->pm_sc.pm_reloadcount;
+ KASSERT(pp->pp_pmcs[ri].pp_pmcval > 0 &&
+ pp->pp_pmcs[ri].pp_pmcval <=
+ pm->pm_sc.pm_reloadcount,
+ ("[pmc,%d] pp_pmcval outside of expected "
+ "range cpu=%d ri=%d pp_pmcval=%jx "
+ "pm_reloadcount=%jx", __LINE__, cpu, ri,
+ pp->pp_pmcs[ri].pp_pmcval,
+ pm->pm_sc.pm_reloadcount));
mtx_pool_unlock_spin(pmc_mtxpool, pm);
} else {
+ tmp = newvalue - PMC_PCPU_SAVED(cpu,ri);
+
+ PMCDBG3(CSW,SWO,1,"cpu=%d ri=%d tmp=%jd (count)",
+ cpu, ri, tmp);
/*
* For counting process-virtual PMCs,

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