diff --git a/README.md b/README.md
index d8b03dc..ddced01 100644
--- a/README.md
+++ b/README.md
@@ -133,13 +133,14 @@ in-memory hash table.
The work of wait event statistics collector worker is controlled by following
GUCs.
-| Parameter name | Data type | Description | Default value |
-| ----------------------------------- | --------- | ------------------------------------------- | ------------: |
-| pg_wait_sampling.history_size | int4 | Size of history in-memory ring buffer | 5000 |
-| pg_wait_sampling.history_period | int4 | Period for history sampling in milliseconds | 10 |
-| pg_wait_sampling.profile_period | int4 | Period for profile sampling in milliseconds | 10 |
-| pg_wait_sampling.profile_pid | bool | Whether profile should be per pid | true |
-| pg_wait_sampling.profile_queries | bool | Whether profile should be per query | true |
+| Parameter name | Data type | Description | Default value |
+|----------------------------------| --------- |---------------------------------------------|--------------:|
+| pg_wait_sampling.history_size | int4 | Size of history in-memory ring buffer | 5000 |
+| pg_wait_sampling.history_period | int4 | Period for history sampling in milliseconds | 10 |
+| pg_wait_sampling.profile_period | int4 | Period for profile sampling in milliseconds | 10 |
+| pg_wait_sampling.profile_pid | bool | Whether profile should be per pid | true |
+| pg_wait_sampling.profile_queries | bool | Whether profile should be per query | true |
+| pg_wait_sampling.sample_cpu | bool | Whether on CPU backends should be sampled | true |
If `pg_wait_sampling.profile_pid` is set to false, sampling profile wouldn't be
collected in per-process manner. In this case the value of pid could would
@@ -148,6 +149,10 @@ be always zero and corresponding row contain samples among all the processes.
While `pg_wait_sampling.profile_queries` is set to false `queryid` field in
views will be zero.
+If `pg_wait_sampling.sample_cpu` is set to true then processes that are not
+waiting on anything are also sampled. The wait event columns for such processes
+will be NULL.
+
These GUCs are allowed to be changed by superuser. Also, they are placed into
shared memory. Thus, they could be changed from any backend and affects worker
runtime.
diff --git a/collector.c b/collector.c
index dcb9695..215bebc 100644
--- a/collector.c
+++ b/collector.c
@@ -163,10 +163,7 @@ probe_waits(History *observations, HTAB *profile_hash,
*observation;
PGPROC *proc = &ProcGlobal->allProcs[i];
- if (proc->pid == 0)
- continue;
-
- if (proc->wait_event_info == 0)
+ if (!pgws_should_sample_proc(proc))
continue;
/* Collect next wait event sample */
diff --git a/pg_wait_sampling.c b/pg_wait_sampling.c
index 268b40e..f226728 100644
--- a/pg_wait_sampling.c
+++ b/pg_wait_sampling.c
@@ -198,7 +198,8 @@ setup_gucs()
history_period_found = false,
profile_period_found = false,
profile_pid_found = false,
- profile_queries_found = false;
+ profile_queries_found = false,
+ sample_cpu_found = false;
get_guc_variables_compat(&guc_vars, &numOpts);
@@ -240,6 +241,12 @@ setup_gucs()
var->_bool.variable = &pgws_collector_hdr->profileQueries;
pgws_collector_hdr->profileQueries = true;
}
+ else if (!strcmp(name, "pg_wait_sampling.sample_cpu"))
+ {
+ sample_cpu_found = true;
+ var->_bool.variable = &pgws_collector_hdr->sampleCpu;
+ pgws_collector_hdr->sampleCpu = true;
+ }
}
if (!history_size_found)
@@ -272,11 +279,18 @@ setup_gucs()
&pgws_collector_hdr->profileQueries, true,
PGC_SUSET, 0, shmem_bool_guc_check_hook, NULL, NULL);
+ if (!sample_cpu_found)
+ DefineCustomBoolVariable("pg_wait_sampling.sample_cpu",
+ "Sets whether not waiting backends should be sampled.", NULL,
+ &pgws_collector_hdr->sampleCpu, true,
+ PGC_SUSET, 0, shmem_bool_guc_check_hook, NULL, NULL);
+
if (history_size_found
|| history_period_found
|| profile_period_found
|| profile_pid_found
- || profile_queries_found)
+ || profile_queries_found
+ || sample_cpu_found)
{
ProcessConfigFile(PGC_SIGHUP);
}
@@ -436,6 +450,28 @@ search_proc(int pid)
return NULL;
}
+/*
+ * Decide whether this PGPROC entry should be included in profiles and output
+ * views.
+ */
+bool
+pgws_should_sample_proc(PGPROC *proc)
+{
+ if (proc->wait_event_info == 0 && !pgws_collector_hdr->sampleCpu)
+ return false;
+
+ /*
+ * On PostgreSQL versions < 17 the PGPROC->pid field is not reset on
+ * process exit. This would lead to such processes getting counted for
+ * null wait events. So instead we make use of DisownLatch() resetting
+ * owner_pid during ProcKill().
+ */
+ if (proc->pid == 0 || proc->procLatch.owner_pid == 0 || proc->pid == MyProcPid)
+ return false;
+
+ return true;
+}
+
typedef struct
{
HistoryItem *items;
@@ -501,13 +537,13 @@ pg_wait_sampling_get_current(PG_FUNCTION_ARGS)
{
PGPROC *proc = &ProcGlobal->allProcs[i];
- if (proc != NULL && proc->pid != 0 && proc->wait_event_info)
- {
- params->items[j].pid = proc->pid;
- params->items[j].wait_event_info = proc->wait_event_info;
- params->items[j].queryId = pgws_proc_queryids[i];
- j++;
- }
+ if (!pgws_should_sample_proc(proc))
+ continue;
+
+ params->items[j].pid = proc->pid;
+ params->items[j].wait_event_info = proc->wait_event_info;
+ params->items[j].queryId = pgws_proc_queryids[i];
+ j++;
}
funcctx->max_calls = j;
}
diff --git a/pg_wait_sampling.h b/pg_wait_sampling.h
index 29425fc..8ff31f8 100644
--- a/pg_wait_sampling.h
+++ b/pg_wait_sampling.h
@@ -68,6 +68,7 @@ typedef struct
int profilePeriod;
bool profilePid;
bool profileQueries;
+ bool sampleCpu;
} CollectorShmqHeader;
/* pg_wait_sampling.c */
@@ -75,6 +76,7 @@ extern CollectorShmqHeader *pgws_collector_hdr;
extern shm_mq *pgws_collector_mq;
extern uint64 *pgws_proc_queryids;
extern void pgws_init_lock_tag(LOCKTAG *tag, uint32 lock);
+extern bool pgws_should_sample_proc(PGPROC *proc);
/* collector.c */
extern void pgws_register_wait_collector(void);
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