1 files changed, 110 insertions, 0 deletions
diff --git a/src/backend/utils/activity/pgstat_bgwriter.c b/src/backend/utils/activity/pgstat_bgwriter.c
new file mode 100644
index 0000000..fbb1edc
--- /dev/null
+++ b/src/backend/utils/activity/pgstat_bgwriter.c
@@ -0,0 +1,110 @@
+/* -------------------------------------------------------------------------
+ *
+ * pgstat_bgwriter.c
+ *	  Implementation of bgwriter statistics.
+ *
+ * This file contains the implementation of bgwriter statistics. It is kept
+ * separate from pgstat.c to enforce the line between the statistics access /
+ * storage implementation and the details about individual types of
+ * statistics.
+ *
+ * Copyright (c) 2001-2022, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/activity/pgstat_bgwriter.c
+ * -------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "utils/pgstat_internal.h"
+
+
+PgStat_BgWriterStats PendingBgWriterStats = {0};
+
+
+/*
+ * Report bgwriter statistics
+ */
+void
+pgstat_report_bgwriter(void)
+{
+	PgStatShared_BgWriter *stats_shmem = &pgStatLocal.shmem->bgwriter;
+	static const PgStat_BgWriterStats all_zeroes;
+
+	Assert(!pgStatLocal.shmem->is_shutdown);
+	pgstat_assert_is_up();
+
+	/*
+	 * This function can be called even if nothing at all has happened. In
+	 * this case, avoid unnecessarily modifying the stats entry.
+	 */
+	if (memcmp(&PendingBgWriterStats, &all_zeroes, sizeof(all_zeroes)) == 0)
+		return;
+
+	pgstat_begin_changecount_write(&stats_shmem->changecount);
+
+#define BGWRITER_ACC(fld) stats_shmem->stats.fld += PendingBgWriterStats.fld
+	BGWRITER_ACC(buf_written_clean);
+	BGWRITER_ACC(maxwritten_clean);
+	BGWRITER_ACC(buf_alloc);
+#undef BGWRITER_ACC
+
+	pgstat_end_changecount_write(&stats_shmem->changecount);
+
+	/*
+	 * Clear out the statistics buffer, so it can be re-used.
+	 */
+	MemSet(&PendingBgWriterStats, 0, sizeof(PendingBgWriterStats));
+}
+
+/*
+ * Support function for the SQL-callable pgstat* functions. Returns
+ * a pointer to the bgwriter statistics struct.
+ */
+PgStat_BgWriterStats *
+pgstat_fetch_stat_bgwriter(void)
+{
+	pgstat_snapshot_fixed(PGSTAT_KIND_BGWRITER);
+
+	return &pgStatLocal.snapshot.bgwriter;
+}
+
+void
+pgstat_bgwriter_reset_all_cb(TimestampTz ts)
+{
+	PgStatShared_BgWriter *stats_shmem = &pgStatLocal.shmem->bgwriter;
+
+	/* see explanation above PgStatShared_BgWriter for the reset protocol */
+	LWLockAcquire(&stats_shmem->lock, LW_EXCLUSIVE);
+	pgstat_copy_changecounted_stats(&stats_shmem->reset_offset,
+									&stats_shmem->stats,
+									sizeof(stats_shmem->stats),
+									&stats_shmem->changecount);
+	stats_shmem->stats.stat_reset_timestamp = ts;
+	LWLockRelease(&stats_shmem->lock);
+}
+
+void
+pgstat_bgwriter_snapshot_cb(void)
+{
+	PgStatShared_BgWriter *stats_shmem = &pgStatLocal.shmem->bgwriter;
+	PgStat_BgWriterStats *reset_offset = &stats_shmem->reset_offset;
+	PgStat_BgWriterStats reset;
+
+	pgstat_copy_changecounted_stats(&pgStatLocal.snapshot.bgwriter,
+									&stats_shmem->stats,
+									sizeof(stats_shmem->stats),
+									&stats_shmem->changecount);
+
+	LWLockAcquire(&stats_shmem->lock, LW_SHARED);
+	memcpy(&reset, reset_offset, sizeof(stats_shmem->stats));
+	LWLockRelease(&stats_shmem->lock);
+
+	/* compensate by reset offsets */
+#define BGWRITER_COMP(fld) pgStatLocal.snapshot.bgwriter.fld -= reset.fld;
+	BGWRITER_COMP(buf_written_clean);
+	BGWRITER_COMP(maxwritten_clean);
+	BGWRITER_COMP(buf_alloc);
+#undef BGWRITER_COMP
+}