sar: A_NET_SOFT: Fix how average backlog length is calculated

Backlog length is an instantaneous value, not a value calculated over the time interval. Its average value should be calculated in a specific way. Signed-off-by: Sebastien GODARD <[email protected]>
sysstat · Mar 27, 2022 · d653467 · d653467
1 parent 690afe9
commit d653467
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Showing 3 changed files with 74 additions and 5 deletions.
diff --git a/activity.c b/activity.c
@@ -1834,7 +1834,7 @@ struct activity softnet_act = {
 #endif
 #ifdef SOURCE_SAR
  .f_print = print_softnet_stats,
- .f_print_avg = print_softnet_stats,
+ .f_print_avg = print_avg_softnet_stats,
 #endif
 #if defined(SOURCE_SAR) || defined(SOURCE_SADF)
  .hdr_line = "CPU;total/s;dropd/s;squeezd/s;rx_rps/s;flw_lim/s;blg_len",

diff --git a/pr_stats.c b/pr_stats.c
@@ -3007,16 +3007,19 @@ __print_funct_t print_fchost_stats(struct activity *a, int prev, int curr,
  * @prev Index in array where stats used as reference are.
  * @curr Index in array for current sample statistics.
  * @itv Interval of time in 1/100th of a second.
+ * @dispavg True if displaying average statistics.
  ***************************************************************************
  */
-__print_funct_t print_softnet_stats(struct activity *a, int prev, int curr,
-  unsigned long long itv)
+__print_funct_t stub_print_softnet_stats(struct activity *a, int prev, int curr,
+  unsigned long long itv, int dispavg)
 {
  int i;
  struct stats_softnet
  *ssnc = (struct stats_softnet *) a->buf[curr],
  *ssnp = (struct stats_softnet *) a->buf[prev];
  unsigned char offline_cpu_bitmap[BITMAP_SIZE(NR_CPUS)] = {0};
+ static __nr_t nr_alloc = 0;
+ static unsigned long long *avg_blg_len = NULL;
 
  if (dish || DISPLAY_ZERO_OMIT(flags)) {
  print_hdr_line(timestamp[!curr], a, FIRST, 7, 9, NULL);
@@ -3033,6 +3036,18 @@ __print_funct_t print_softnet_stats(struct activity *a, int prev, int curr,
  a->nr_ini = a->nr[curr];
  }
 
+ /* Allocate array for CPU backlog lengths */
+ if (!avg_blg_len || (a->nr_ini > nr_alloc)) {
+ SREALLOC(avg_blg_len, unsigned long long, sizeof(unsigned long long) * a->nr_ini);
+
+ if (a->nr_ini > nr_alloc) {
+ /* Init additional space allocated */
+ memset(avg_blg_len + nr_alloc, 0,
+ sizeof(unsigned long long) * (a->nr_ini - nr_alloc));
+ }
+ nr_alloc = a->nr_ini;
+ }
+
  /* Compute statistics for CPU "all" */
  get_global_soft_statistics(a, prev, curr, flags, offline_cpu_bitmap);
 
@@ -3078,10 +3093,62 @@ __print_funct_t print_softnet_stats(struct activity *a, int prev, int curr,
  S_VALUE(ssnp->time_squeeze, ssnc->time_squeeze, itv),
  S_VALUE(ssnp->received_rps, ssnc->received_rps, itv),
  S_VALUE(ssnp->flow_limit, ssnc->flow_limit, itv));
- cprintf_u64(NO_UNIT, 1, 9,
- (unsigned long long) ssnc->backlog_len);
+ if (!dispavg) {
+ /* Display instantaneous value */
+ cprintf_u64(NO_UNIT, 1, 9,
+ (unsigned long long) ssnc->backlog_len);
+
+ /* Used to compute average value */
+ avg_blg_len[i] += (unsigned long long ) ssnc->backlog_len;
+ }
+ else {
+ /* Display average value */
+ cprintf_f(NO_UNIT, 1, 9, 0,
+ (double) avg_blg_len[i] / avg_count);
+ }
+
  printf("\n");
  }
+
+ if (dispavg && avg_blg_len) {
+ free(avg_blg_len);
+ avg_blg_len = NULL;
+ nr_alloc = 0;
+ }
+}
+
+/*
+ ***************************************************************************
+ * Display softnet statistics.
+ *
+ * IN:
+ * @a Activity structure with statistics.
+ * @prev Index in array where stats used as reference are.
+ * @curr Index in array for current sample statistics.
+ * @itv Interval of time in 1/100th of a second.
+ ***************************************************************************
+ */
+__print_funct_t print_softnet_stats(struct activity *a, int prev, int curr,
+ unsigned long long itv)
+{
+ stub_print_softnet_stats(a, prev, curr, itv, FALSE);
+}
+
+/*
+ ***************************************************************************
+ * Display average softnet statistics.
+ *
+ * IN:
+ * @a Activity structure with statistics.
+ * @prev Index in array where stats used as reference are.
+ * @curr Index in array for current sample statistics.
+ * @itv Interval of time in 1/100th of a second.
+ ***************************************************************************
+ */
+__print_funct_t print_avg_softnet_stats(struct activity *a, int prev, int curr,
+ unsigned long long itv)
+{
+ stub_print_softnet_stats(a, prev, curr, itv, TRUE);
 }
 
 /*

diff --git a/pr_stats.h b/pr_stats.h
@@ -126,6 +126,8 @@ __print_funct_t print_avg_pwr_usb_stats
  (struct activity *, int, int, unsigned long long);
 __print_funct_t print_avg_filesystem_stats
  (struct activity *, int, int, unsigned long long);
+__print_funct_t print_avg_softnet_stats
+ (struct activity *, int, int, unsigned long long);
 __print_funct_t print_avg_psicpu_stats
  (struct activity *, int, int, unsigned long long);
 __print_funct_t print_avg_psiio_stats