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If R (runqueue) is greater in B (waitqueue) in vmstat, is is I/O bound?
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If the runqueue is the number of processes waiting for their turn on the CPU + processes currently running, and waitqueue is the number of processes waiting for I/O, then wouldn’t B in the vmstat output being greater than R mean that there is an I/O bound, not CPU bound? I am confused because the link below says the opposite ...
From http://nonfunctionaltestingtools.blogspot.com/2013/03/vmstat-output-explained.html?m=1
“If runnable threads (r) divided by the number of CPU is greater than one -> possible CPU bottleneck (The (r) coulmn should be compared with number of CPUs (logical CPUs as in uptime) if we have enough CPUs or we have more threads.) High numbers in the blocked processes column (b) indicates slow disks. (r) should always be higher than (b); if it is not, it usually means you have a CPU bottleneckâ€Â
cpu-usage
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John Alvarez
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If the runqueue is the number of processes waiting for their turn on the CPU + processes currently running, and waitqueue is the number of processes waiting for I/O, then wouldn’t B in the vmstat output being greater than R mean that there is an I/O bound, not CPU bound? I am confused because the link below says the opposite ...
From http://nonfunctionaltestingtools.blogspot.com/2013/03/vmstat-output-explained.html?m=1
“If runnable threads (r) divided by the number of CPU is greater than one -> possible CPU bottleneck (The (r) coulmn should be compared with number of CPUs (logical CPUs as in uptime) if we have enough CPUs or we have more threads.) High numbers in the blocked processes column (b) indicates slow disks. (r) should always be higher than (b); if it is not, it usually means you have a CPU bottleneckâ€Â
cpu-usage
asked 3 hours ago
John Alvarez
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John Alvarez is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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up vote
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down vote
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up vote
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down vote
favorite
If the runqueue is the number of processes waiting for their turn on the CPU + processes currently running, and waitqueue is the number of processes waiting for I/O, then wouldn’t B in the vmstat output being greater than R mean that there is an I/O bound, not CPU bound? I am confused because the link below says the opposite ...
From http://nonfunctionaltestingtools.blogspot.com/2013/03/vmstat-output-explained.html?m=1
“If runnable threads (r) divided by the number of CPU is greater than one -> possible CPU bottleneck (The (r) coulmn should be compared with number of CPUs (logical CPUs as in uptime) if we have enough CPUs or we have more threads.) High numbers in the blocked processes column (b) indicates slow disks. (r) should always be higher than (b); if it is not, it usually means you have a CPU bottleneckâ€Â
cpu-usage
asked 3 hours ago
John Alvarez
61
New contributor
John Alvarez is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
If the runqueue is the number of processes waiting for their turn on the CPU + processes currently running, and waitqueue is the number of processes waiting for I/O, then wouldn’t B in the vmstat output being greater than R mean that there is an I/O bound, not CPU bound? I am confused because the link below says the opposite ...
From http://nonfunctionaltestingtools.blogspot.com/2013/03/vmstat-output-explained.html?m=1
“If runnable threads (r) divided by the number of CPU is greater than one -> possible CPU bottleneck (The (r) coulmn should be compared with number of CPUs (logical CPUs as in uptime) if we have enough CPUs or we have more threads.) High numbers in the blocked processes column (b) indicates slow disks. (r) should always be higher than (b); if it is not, it usually means you have a CPU bottleneckâ€Â
cpu-usage
cpu-usage
asked 3 hours ago
John Alvarez
61
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John Alvarez is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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asked 3 hours ago
John Alvarez
61
New contributor
John Alvarez is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 3 hours ago
John Alvarez
61
New contributor
John Alvarez is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 3 hours ago
John Alvarez
61
asked 3 hours ago
John Alvarez
61
61
New contributor
John Alvarez is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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New contributor
John Alvarez is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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John Alvarez is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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1 Answer
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A higher number in b than in r means the CPUs are often idle, so you are right being confused. The document should have read 'means you have an I/O bottleneck'.
Beware that is says r should never be higher than the number of CPUs, and r=16 on a 12 CPU system is a "serious" problem. This is quite exaggerated. That just means CPUs are fully used and some threads are waiting. Usually no big deal.
Finally, don't confuse threads and processes, like the linked document sometimes does too. The r and b columns show number of threads, not processes. Not all processes are single threaded.
answered 2 hours ago
jlliagre
45.4k680129
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1 Answer
1
active
oldest
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1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
2
down vote
A higher number in b than in r means the CPUs are often idle, so you are right being confused. The document should have read 'means you have an I/O bottleneck'.
Beware that is says r should never be higher than the number of CPUs, and r=16 on a 12 CPU system is a "serious" problem. This is quite exaggerated. That just means CPUs are fully used and some threads are waiting. Usually no big deal.
Finally, don't confuse threads and processes, like the linked document sometimes does too. The r and b columns show number of threads, not processes. Not all processes are single threaded.
answered 2 hours ago
jlliagre
45.4k680129
add a comment |Â
up vote
2
down vote
A higher number in b than in r means the CPUs are often idle, so you are right being confused. The document should have read 'means you have an I/O bottleneck'.
Beware that is says r should never be higher than the number of CPUs, and r=16 on a 12 CPU system is a "serious" problem. This is quite exaggerated. That just means CPUs are fully used and some threads are waiting. Usually no big deal.
Finally, don't confuse threads and processes, like the linked document sometimes does too. The r and b columns show number of threads, not processes. Not all processes are single threaded.
answered 2 hours ago
jlliagre
45.4k680129
add a comment |Â
up vote
2
down vote
up vote
2
down vote
A higher number in b than in r means the CPUs are often idle, so you are right being confused. The document should have read 'means you have an I/O bottleneck'.
Beware that is says r should never be higher than the number of CPUs, and r=16 on a 12 CPU system is a "serious" problem. This is quite exaggerated. That just means CPUs are fully used and some threads are waiting. Usually no big deal.
Finally, don't confuse threads and processes, like the linked document sometimes does too. The r and b columns show number of threads, not processes. Not all processes are single threaded.
answered 2 hours ago
jlliagre
45.4k680129
A higher number in b than in r means the CPUs are often idle, so you are right being confused. The document should have read 'means you have an I/O bottleneck'.
Beware that is says r should never be higher than the number of CPUs, and r=16 on a 12 CPU system is a "serious" problem. This is quite exaggerated. That just means CPUs are fully used and some threads are waiting. Usually no big deal.
Finally, don't confuse threads and processes, like the linked document sometimes does too. The r and b columns show number of threads, not processes. Not all processes are single threaded.
answered 2 hours ago
jlliagre
45.4k680129
answered 2 hours ago
jlliagre
45.4k680129
answered 2 hours ago
jlliagre
45.4k680129
answered 2 hours ago
jlliagre
45.4k680129
45.4k680129
add a comment |Â
add a comment |Â
John Alvarez is a new contributor. Be nice, and check out our Code of Conduct.
John Alvarez is a new contributor. Be nice, and check out our Code of Conduct.
John Alvarez is a new contributor. Be nice, and check out our Code of Conduct.
John Alvarez is a new contributor. Be nice, and check out our Code of Conduct.
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