2026-03-12 20:23:15

tpt/schedlat.sql

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+-- Copyright 2020 Tanel Poder. All rights reserved. More info at https://tanelpoder.com
+-- Licensed under the Apache License, Version 2.0. See LICENSE.txt for terms and conditions.
+
+-- Name:    schedlat.sql
+-- Purpose: List PSP0 process scheduling latency test results (where scheduling latency is not 0)
+-- Other:   Oracle 12c+ PSP0 process regularly (voluntarily) goes to sleep for 1000 microseconds
+--          taking a high resolution system timestamp just before going to sleep and right after
+--          getting back onto CPU. Usin these timestamps it checks if it managed to wake up 
+--          "exactly" 1000 usec later or
+
+PROMPT Listing recent non-zero scheduling delays from X$KSO_SCHED_DELAY_HISTORY
+
+SELECT 
+    MIN(sample_start_time) history_begin_time, MAX(sample_end_time) history_end_time
+  , MAX(sched_delay_micro) max_latency_us
+  , AVG(sched_delay_micro) avg_latency_us
+FROM
+    sys.x$kso_sched_delay_history
+/
+
+PROMPT Any noticed scheduling delays during the in-memory history window are listed below:
+
+SELECT 
+    sample_start_time
+  , sample_end_time
+  , sched_delay_micro
+FROM
+    sys.x$kso_sched_delay_history
+WHERE
+    sched_delay_micro != 0
+/
+