processes plugin: Fix counters initialization / spikes

processes plugin generates spikes on (re)start. That is caused by
wrong counter logic: When collectd (re)started, monitored processes,
which was started before collectd, have non-zero values in
cpu_user/cpu_system/vmem_minflt/vmem_majflt, so `want_init` is false.
What produces spike.
At other hand, processes which are started between read cycles, should
be fully accounted without initialization. So, we must skip only first
cycle for these counters.

diff --git a/src/processes.c b/src/processes.c
index 8ac05a3..8958c0c 100644 (file)
--- a/src/processes.c
+++ b/src/processes.c
@@ -225,6 +225,7 @@ typedef struct procstat
 
 static procstat_t *list_head_g = NULL;
 
+static _Bool want_init = 1;
 static _Bool report_ctx_switch = 0;
 
 #if HAVE_THREAD_INFO
@@ -362,13 +363,16 @@ static int ps_list_match (const char *name, const char *cmdline, procstat_t *ps)
        return (0);
 } /* int ps_list_match */
 
-static void ps_update_counter (_Bool init, derive_t *group_counter,
+static void ps_update_counter (derive_t *group_counter,
                                derive_t *curr_counter, derive_t new_counter)
 {
        unsigned long curr_value;
        
-       if (init)
+       if (want_init)
+       {
+               *curr_counter = new_counter;
                return;
+       }
 
        if (new_counter < *curr_counter)
                curr_value = new_counter + (ULONG_MAX - *curr_counter);
@@ -389,8 +393,6 @@ static void ps_list_add (const char *name, const char *cmdline, procstat_entry_t
 
        for (procstat_t *ps = list_head_g; ps != NULL; ps = ps->next)
        {
-               _Bool want_init;
-
                if ((ps_list_match (name, cmdline, ps)) == 0)
                        continue;
 
@@ -446,24 +448,20 @@ static void ps_list_add (const char *name, const char *cmdline, procstat_entry_t
                ps->cswitch_vol   += ((pse->cswitch_vol == -1)?0:pse->cswitch_vol);
                ps->cswitch_invol += ((pse->cswitch_invol == -1)?0:pse->cswitch_invol);
 
-               want_init = (entry->vmem_minflt_counter == 0)
-                               && (entry->vmem_majflt_counter == 0);
-               ps_update_counter (want_init,
+               ps_update_counter (
                                &ps->vmem_minflt_counter,
                                &pse->vmem_minflt_counter,
                                entry->vmem_minflt_counter);
-               ps_update_counter (want_init,
+               ps_update_counter (
                                &ps->vmem_majflt_counter,
                                &pse->vmem_majflt_counter,
                                entry->vmem_majflt_counter);
 
-               want_init = (entry->cpu_user_counter == 0)
-                               && (entry->cpu_system_counter == 0);
-               ps_update_counter (want_init,
+               ps_update_counter (
                                &ps->cpu_user_counter,
                                &pse->cpu_user_counter,
                                entry->cpu_user_counter);
-               ps_update_counter (want_init,
+               ps_update_counter (
                                &ps->cpu_system_counter,
                                &pse->cpu_system_counter,
                                entry->cpu_system_counter);
@@ -2395,6 +2393,8 @@ static int ps_read (void)
        read_fork_rate();
 #endif /* KERNEL_SOLARIS */
 
+       want_init = 0;
+
        return (0);
 } /* int ps_read */