diff --git a/pg_stat_monitor.c b/pg_stat_monitor.c
index 941cb1d..67462f3 100644
--- a/pg_stat_monitor.c
+++ b/pg_stat_monitor.c
@@ -35,6 +35,9 @@ PG_MODULE_MAGIC;
 
 #define PGUNSIXBIT(val) (((val) & 0x3F) + '0')
 
+#define _memset(_dst,_val,_size)\
+        memset((void*)_dst, _val, _size);
+
 #define _snprintf(_str_dst, _str_src, _len, _max_len)\
   memcpy((void *)_str_dst, _str_src, _len < _max_len ? _len : _max_len)
 
@@ -1344,33 +1347,41 @@ pgss_update_entry(pgssEntry *entry,
 			_snprintf(e->counters.error.message, error_info->message, message_len, ERROR_MESSAGE_LEN);
 		}
 		e->counters.calls.rows += rows;
-		if (bufusage)
-		{
-			e->counters.blocks.shared_blks_hit += bufusage->shared_blks_hit;
-			e->counters.blocks.shared_blks_read += bufusage->shared_blks_read;
-			e->counters.blocks.shared_blks_dirtied += bufusage->shared_blks_dirtied;
-			e->counters.blocks.shared_blks_written += bufusage->shared_blks_written;
-			e->counters.blocks.local_blks_hit += bufusage->local_blks_hit;
-			e->counters.blocks.local_blks_read += bufusage->local_blks_read;
-			e->counters.blocks.local_blks_dirtied += bufusage->local_blks_dirtied;
-			e->counters.blocks.local_blks_written += bufusage->local_blks_written;
-			e->counters.blocks.temp_blks_read += bufusage->temp_blks_read;
-			e->counters.blocks.temp_blks_written += bufusage->temp_blks_written;
-			e->counters.blocks.blk_read_time += INSTR_TIME_GET_MILLISEC(bufusage->blk_read_time);
-			e->counters.blocks.blk_write_time += INSTR_TIME_GET_MILLISEC(bufusage->blk_write_time);
-		}
+
+        if (e->counters.calls.calls == 0)
+        {
+          _memset(&e->counters.walusage, 0, sizeof(e->counters.walusage));
+        }
+        if (e->counters.calls.calls > 0)
+        {
+		    if (bufusage)
+		    {
+		        e->counters.blocks.shared_blks_hit += (int64)(bufusage->shared_blks_hit - e->counters.blocks.shared_blks_hit)/e->counters.calls.calls;
+			    e->counters.blocks.shared_blks_read += (int64)(bufusage->shared_blks_read - e->counters.blocks.shared_blks_read)/e->counters.calls.calls;
+			    e->counters.blocks.shared_blks_dirtied += (int64)(bufusage->shared_blks_dirtied - e->counters.blocks.shared_blks_dirtied)/e->counters.calls.calls;
+			    e->counters.blocks.shared_blks_written += (int64)(bufusage->shared_blks_written - e->counters.blocks.shared_blks_written)/e->counters.calls.calls;
+			    e->counters.blocks.local_blks_hit += (int64)(bufusage->local_blks_hit - e->counters.blocks.local_blks_hit)/e->counters.calls.calls;
+			    e->counters.blocks.local_blks_read += (int64)(bufusage->local_blks_read - e->counters.blocks.local_blks_read)/e->counters.calls.calls;
+			    e->counters.blocks.local_blks_dirtied += (int64)(bufusage->local_blks_dirtied - e->counters.blocks.local_blks_dirtied)/e->counters.calls.calls;
+			    e->counters.blocks.local_blks_written += (int64)(bufusage->local_blks_written - e->counters.blocks.local_blks_written)/e->counters.calls.calls;
+			    e->counters.blocks.temp_blks_read += (int64)(bufusage->temp_blks_read - e->counters.blocks.temp_blks_read)/e->counters.calls.calls;
+			    e->counters.blocks.temp_blks_written += (int64)(bufusage->temp_blks_written - e->counters.blocks.temp_blks_written)/e->counters.calls.calls;
+			    e->counters.blocks.blk_read_time += (int64)(INSTR_TIME_GET_MILLISEC(bufusage->blk_read_time) - e->counters.blocks.blk_read_time)/e->counters.calls.calls;
+			    e->counters.blocks.blk_write_time += (int64)(INSTR_TIME_GET_MILLISEC(bufusage->blk_write_time) - e->counters.blocks.blk_write_time)/e->counters.calls.calls;
+            }
+		    if (sys_info)
+		    {
+			    e->counters.sysinfo.utime = (int64)(sys_info->utime - e->counters.sysinfo.utime)/e->counters.calls.calls;
+			    e->counters.sysinfo.stime = (int64)(sys_info->stime - e->counters.sysinfo.stime)/e->counters.calls.calls;
+		    }
+		    if (walusage)
+		    {
+			    e->counters.walusage.wal_records +=(int64) (walusage->wal_records - e->counters.walusage.wal_records)/e->counters.calls.calls;
+			    e->counters.walusage.wal_fpi +=(int64) (walusage->wal_fpi - e->counters.walusage.wal_fpi)/e->counters.calls.calls;
+                e->counters.walusage.wal_bytes += (int64)( walusage->wal_bytes - e->counters.walusage.wal_bytes)/e->counters.calls.calls;
+            }
+        }
 		e->counters.calls.usage += USAGE_EXEC(total_time);
-		if (sys_info)
-		{
-			e->counters.sysinfo.utime += sys_info->utime;
-			e->counters.sysinfo.stime += sys_info->stime;
-		}
-		if (walusage)
-		{
-			e->counters.walusage.wal_records += walusage->wal_records;
-			e->counters.walusage.wal_fpi += walusage->wal_fpi;
-			e->counters.walusage.wal_bytes += walusage->wal_bytes;
-		}
 		SpinLockRelease(&e->mutex);
 	}
 }