iotop reports high IO wait percentages
Issue
- iotop reports high IO wait percentages:
TIME TID PRIO USER DISK READ DISK WRITE SWAPIN IO COMMAND
14:09:54 16360 be/3 root 0.00 B/s 0.00 B/s 0.00 % 90.79 % [jbd2/dm-14-8]
14:09:54 1782 be/3 root 0.00 B/s 3.62 K/s 0.00 % 0.28 % [jbd2/dm-9-8]
14:09:54 17099 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.01 % [jbd2/dm-17-8]
14:09:54 16748 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.01 % [jbd2/dm-16-8]
...
TIME TID PRIO USER DISK READ DISK WRITE SWAPIN IO COMMAND
14:10:19 16360 be/3 root 0.00 B/s 1502.84 K/s 0.00 % 99.99 % [jbd2/dm-14-8]
14:10:19 1782 be/3 root 0.00 B/s 2.89 K/s 0.00 % 6.36 % [jbd2/dm-9-8]
14:10:19 17219 be/4 root 0.00 B/s 0.00 B/s 0.00 % 3.75 % [flush-253:14]
...
- top reports high iowait times for one CPU:
top - 14:10:06 up 2 days, 12:58, 6 users, load average: 379.38, 85.43, 28.27
Tasks: 1908 total, 1 running, 1907 sleeping, 0 stopped, 0 zombie
Cpu0 : 1.0%us, 7.5%sy, 0.0%ni, 91.5%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu1 : 1.2%us, 8.5%sy, 0.0%ni, 90.3%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu2 : 1.4%us, 3.4%sy, 0.0%ni, 95.2%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu3 : 4.2%us, 2.0%sy, 0.0%ni, 93.8%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu4 : 1.4%us, 5.2%sy, 0.0%ni, 93.4%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu5 : 1.0%us, 2.6%sy, 0.0%ni, 0.0%id, 96.4%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu6 : 0.6%us, 2.0%sy, 0.0%ni, 97.0%id, 0.4%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu7 : 1.2%us, 4.0%sy, 0.0%ni, 94.8%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 32692068k total, 31517304k used, 1174764k free, 348624k buffers
Swap: 18874360k total, 0k used, 18874360k free, 21002128k cached
Environment
- Red Hat Enterprise Linux 6.5
- ext3/4
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