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CPU Usage Gets Doubled After OS Reboot (Doc ID 2379576.1)

Last updated on AUGUST 04, 2018

Applies to:

Oracle Database - Enterprise Edition - Version 11.2.0.4 and later
Linux x86-64

Symptoms

1. After the DB server restarted, the OS CPU usage gets doubled:

<<<<< Before restarted >>>>>
zzz ***Wed Mar 7 22:30:09 CST 2018
Tasks: 2468 total, 5 running, 2463 sleeping, 0 stopped, 0 zombie
Cpu(s): 24.8%us, 10.7%sy, 0.0%ni, 61.7%id, 2.0%wa, 0.0%hi, 0.8%si, 0.0%st
Mem: 132120620k total, 129672488k used, 2448132k free, 249472k buffers
Swap: 17301500k total, 1829876k used, 15471624k free, 105717256k cached
zzz ***Wed Mar 7 22:30:39 CST 2018
top - 22:30:40 up 365 days, 4:57, 0 users, load average: 3.86, 4.03, 4.33
Tasks: 2438 total, 2 running, 2436 sleeping, 0 stopped, 0 zombie
Cpu(s): 18.2%us, 7.8%sy, 0.0%ni, 72.6%id, 0.8%wa, 0.0%hi, 0.6%si, 0.0%st
Mem: 132120620k total, 129203136k used, 2917484k free, 249484k buffers
Swap: 17301500k total, 1829876k used, 15471624k free, 105719856k cached
zzz ***Wed Mar 7 22:31:09 CST 2018
Cpu(s): 25.2%us, 11.1%sy, 0.0%ni, 62.0%id, 0.6%wa, 0.0%hi, 1.0%si, 0.0%st
Mem: 132120620k total, 129458052k used, 2662568k free, 249484k buffers
Swap: 17301500k total, 1829876k used, 15471624k free, 105722220k cached
<<<<< After restarted >>>>>
zzz ***Sun Mar 11 22:30:21 CST 2018
top - 22:30:23 up 1 day, 14:43, 0 users, load average: 7.58, 8.30, 8.90
Tasks: 2423 total, 9 running, 2414 sleeping, 0 stopped, 0 zombie
Cpu(s): 39.1%us, 19.8%sy, 0.0%ni, 38.1%id, 0.4%wa, 0.0%hi, 2.6%si, 0.0%st
Mem: 132120620k total, 130462504k used, 1658116k free, 304552k buffers
Swap: 17301500k total, 232k used, 17301268k free, 111346800k cached
zzz ***Sun Mar 11 22:31:21 CST 2018
Cpu(s): 50.6%us, 25.4%sy, 0.0%ni, 22.4%id, 0.4%wa, 0.0%hi, 1.2%si, 0.0%st
Mem: 132120620k total, 130406440k used, 1714180k free, 304560k buffers
Swap: 17301500k total, 232k used, 17301268k free, 111359204k cached
zzz ***Sun Mar 11 22:31:51 CST 2018
Tasks: 2407 total, 7 running, 2400 sleeping, 0 stopped, 0 zombie
Cpu(s): 47.6%us, 23.7%sy, 0.0%ni, 27.0%id, 1.0%wa, 0.0%hi, 0.7%si, 0.0%st
Mem: 132120620k total, 130320832k used, 1799788k free, 304560k buffers
Swap: 17301500k total, 232k used, 17301268k free, 111360944k cached

 2. No SQL plan changes, almost all SQL's CPU Time gets doubled but the buffer gets doesn't change. for example, the top one CPU time SQL:

sql_id plan_hash snap_time executions buffer_gets cpu_time
<<<<< Before restarted >>>>>
5622uh375bj9y 1957741825 2018-3-7 21:00 13722 318910832 189205927
5622uh375bj9y 1957741825 2018-3-7 22:00 12904 301397537 178826702
5622uh375bj9y 1957741825 2018-3-7 23:00 11766 272182540 161232345
<<<<< After restarted >>>>>
5622uh375bj9y 1957741825 2018-3-11 21:00 12709 302640576 526844973
5622uh375bj9y 1957741825 2018-3-11 22:00 11282 264862940 457663459
5622uh375bj9y 1957741825 2018-3-11 23:00 11389 265648944 459996125

 

Changes

 DB Server restarted.

Cause

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