mpstat: Fix values displayed when an offline CPU goes back online

Try to avoid values jumping from zero when an offline CPU goes back
online.

Signed-off-by: Sebastien GODARD <sysstat@users.noreply.github.com>

diff --git a/mpstat.c b/mpstat.c
index 2ad621b5510924a959926ae1f556846f9b0dd667..727a7eaeb46c1f4b91c255ed708e4faa7a0f56d8 100644 (file)
--- a/mpstat.c
+++ b/mpstat.c
@@ -271,6 +271,39 @@ void sfree_mp_struct(void)
        free(cpu2node);
 }
 
+/*
+ ***************************************************************************
+ * Set interrupt values for current sample to those of previous sample.
+ *
+ * IN:
+ * @st_ic      Array for per-CPU interrupts statistics.
+ * @c          Fist CPU to process.
+ * @last       Last CPU to process.
+ * @ic_nr      Number of interrupts (hard or soft) per CPU.
+ * @curr       Position in array where current statistics will be saved.
+ **************************************************************************
+ */
+void fwd_irq_values(struct stats_irqcpu *st_ic[], unsigned int c,
+                   unsigned int last, int ic_nr, int curr)
+{
+       struct stats_irq *st_irq_i, *st_irq_j;
+       struct stats_irqcpu *p, *q;
+       int j;
+
+       while (c < last) {
+               st_irq_i = st_irq[curr] + c + 1;
+               st_irq_j = st_irq[!curr] + c + 1;
+               st_irq_i->irq_nr = st_irq_j->irq_nr;
+
+               for (j = 0; j < ic_nr; j++) {
+                       p = st_ic[curr] + c * ic_nr + j;
+                       q = st_ic[!curr] + c * ic_nr + j;
+                       p->interrupt = q->interrupt;
+               }
+               c++;
+       }
+}
+
 /*
  ***************************************************************************
  * Get node placement (which node each CPU belongs to, and total number of
@@ -1779,16 +1812,10 @@ void read_interrupts_stat(char *file, struct stats_irqcpu *st_ic[], int ic_nr, i
        struct stats_irqcpu *p;
        char *line = NULL, *li;
        unsigned long irq = 0;
-       unsigned int cpu;
+       unsigned int cpu, c = 0;
        int cpu_index[cpu_nr], index = 0, len;
        char *cp, *next;
 
-       /* Reset total number of interrupts received by each CPU */
-       for (cpu = 0; cpu < cpu_nr; cpu++) {
-               st_irq_i = st_irq[curr] + cpu + 1;
-               st_irq_i->irq_nr = 0;
-       }
-
        if ((fp = fopen(file, "r")) != NULL) {
 
                SREALLOC(line, char, INTERRUPTS_LINE + 11 * cpu_nr);
@@ -1801,12 +1828,29 @@ void read_interrupts_stat(char *file, struct stats_irqcpu *st_ic[], int ic_nr, i
                        while (((cp = strstr(next, "CPU")) != NULL) && (index < cpu_nr)) {
                                cpu = strtol(cp + 3, &next, 10);
                                cpu_index[index++] = cpu;
+
+                               /*
+                                * Reset total number of interrupts received by a CPU
+                                * only for online CPU. Only needed for st_irq structures.
+                                */
+                               st_irq_i = st_irq[curr] + cpu + 1;
+                               st_irq_i->irq_nr = 0;
+
+                               /*
+                                * For offline CPU, pick up previous values so that when the
+                                * CPU goes back online, values won't jump from zero.
+                                */
+                               fwd_irq_values(st_ic, c, cpu, ic_nr, curr);
+                               c = cpu + 1;
                        }
                        if (index)
                                /* Header line found */
                                break;
                }
 
+               /* Process possible offline CPU at the end of the list */
+               fwd_irq_values(st_ic, c, cpu_nr, ic_nr, curr);
+
                /* Parse each line of interrupts statistics data */
                while ((fgets(line, INTERRUPTS_LINE + 11 * cpu_nr, fp) != NULL) &&
                       (irq < ic_nr)) {