ps and top give different CPU usage
I've seen a few posts similar to this, most notably here, but wasn't quite satisfied with the answers. I'm comparing top and ps results on a specific process and see huge discrepancies in CPU usage. top varies between <1% and 100% from interval to interval including periods of sustained highs (>50% for 3-4 intervals), while ps is steady at 2.2%. The process I'm watching doesn't have any children or anything, so I'm not quite sure what to make of it. Since there are sustained high periods in top, I feel I can rule out sampling interval.
Is this really just a discrepancy in how these two tools handle I/O wait time, as suggested by the question I linked to above?
EDIT:
I've seen it fluctuate to 2.1% in ps, but that's it so far. Output from top -p 4522:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
4522 root 16 0 340m 316m 4732 R 54.7 1.3 508:57.46 maui
Output from ps u -p 4522:
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 4522 2.2 1.3 348764 324456 ? Ss Aug25 509:25 /usr/local/maui/sbin/maui
linux top ps
edited Mar 20 '17 at 10:17
Community♦
1
asked Sep 10 '13 at 12:40
TTTTTT
182214
add a comment |
I've seen a few posts similar to this, most notably here, but wasn't quite satisfied with the answers. I'm comparing top and ps results on a specific process and see huge discrepancies in CPU usage. top varies between <1% and 100% from interval to interval including periods of sustained highs (>50% for 3-4 intervals), while ps is steady at 2.2%. The process I'm watching doesn't have any children or anything, so I'm not quite sure what to make of it. Since there are sustained high periods in top, I feel I can rule out sampling interval.
Is this really just a discrepancy in how these two tools handle I/O wait time, as suggested by the question I linked to above?
EDIT:
I've seen it fluctuate to 2.1% in ps, but that's it so far. Output from top -p 4522:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
4522 root 16 0 340m 316m 4732 R 54.7 1.3 508:57.46 maui
Output from ps u -p 4522:
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 4522 2.2 1.3 348764 324456 ? Ss Aug25 509:25 /usr/local/maui/sbin/maui
linux top ps
edited Mar 20 '17 at 10:17
Community♦
1
asked Sep 10 '13 at 12:40
TTTTTT
182214
You meanpsnever ever changes and is always 2.2? Could you post the output ofpsandtopfor the command in question so we can have a look?
– terdon
Sep 10 '13 at 13:18
@terdon I updated the original post with additional information.
– TTT
Sep 11 '13 at 13:16
add a comment |
I've seen a few posts similar to this, most notably here, but wasn't quite satisfied with the answers. I'm comparing top and ps results on a specific process and see huge discrepancies in CPU usage. top varies between <1% and 100% from interval to interval including periods of sustained highs (>50% for 3-4 intervals), while ps is steady at 2.2%. The process I'm watching doesn't have any children or anything, so I'm not quite sure what to make of it. Since there are sustained high periods in top, I feel I can rule out sampling interval.
Is this really just a discrepancy in how these two tools handle I/O wait time, as suggested by the question I linked to above?
EDIT:
I've seen it fluctuate to 2.1% in ps, but that's it so far. Output from top -p 4522:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
4522 root 16 0 340m 316m 4732 R 54.7 1.3 508:57.46 maui
Output from ps u -p 4522:
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 4522 2.2 1.3 348764 324456 ? Ss Aug25 509:25 /usr/local/maui/sbin/maui
linux top ps
edited Mar 20 '17 at 10:17
Community♦
1
asked Sep 10 '13 at 12:40
TTTTTT
182214
I've seen a few posts similar to this, most notably here, but wasn't quite satisfied with the answers. I'm comparing top and ps results on a specific process and see huge discrepancies in CPU usage. top varies between <1% and 100% from interval to interval including periods of sustained highs (>50% for 3-4 intervals), while ps is steady at 2.2%. The process I'm watching doesn't have any children or anything, so I'm not quite sure what to make of it. Since there are sustained high periods in top, I feel I can rule out sampling interval.
Is this really just a discrepancy in how these two tools handle I/O wait time, as suggested by the question I linked to above?
EDIT:
I've seen it fluctuate to 2.1% in ps, but that's it so far. Output from top -p 4522:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
4522 root 16 0 340m 316m 4732 R 54.7 1.3 508:57.46 maui
Output from ps u -p 4522:
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 4522 2.2 1.3 348764 324456 ? Ss Aug25 509:25 /usr/local/maui/sbin/maui
linux top ps
linux top ps
edited Mar 20 '17 at 10:17
Community♦
1
asked Sep 10 '13 at 12:40
TTTTTT
182214
edited Mar 20 '17 at 10:17
Community♦
1
asked Sep 10 '13 at 12:40
TTTTTT
182214
edited Mar 20 '17 at 10:17
Community♦
1
edited Mar 20 '17 at 10:17
Community♦
1
edited Mar 20 '17 at 10:17
Community♦
1
1
asked Sep 10 '13 at 12:40
TTTTTT
182214
asked Sep 10 '13 at 12:40
TTTTTT
182214
asked Sep 10 '13 at 12:40
TTTTTT
182214
182214
You meanpsnever ever changes and is always 2.2? Could you post the output ofpsandtopfor the command in question so we can have a look?
– terdon
Sep 10 '13 at 13:18
@terdon I updated the original post with additional information.
– TTT
Sep 11 '13 at 13:16
add a comment |
You meanpsnever ever changes and is always 2.2? Could you post the output ofpsandtopfor the command in question so we can have a look?
– terdon
Sep 10 '13 at 13:18
@terdon I updated the original post with additional information.
– TTT
Sep 11 '13 at 13:16
You mean
ps never ever changes and is always 2.2? Could you post the output of ps and top for the command in question so we can have a look?– terdon
Sep 10 '13 at 13:18
You mean
ps never ever changes and is always 2.2? Could you post the output of ps and top for the command in question so we can have a look?– terdon
Sep 10 '13 at 13:18
@terdon I updated the original post with additional information.
– TTT
Sep 11 '13 at 13:16
@terdon I updated the original post with additional information.
– TTT
Sep 11 '13 at 13:16
add a comment |
2 Answers
2
active
oldest
votes
The likeliest reason is that top shows the percentage values as a percentage of a single CPU while ps shows the percentage of total available CPU power. Try running top and hitting ShiftI while it's running to show the percentage of all cores.
If this is a server cluster with a lot of CPUs, what you describe is normal behavior. Also see here.
edited Mar 20 '17 at 10:16
Community♦
1
answered Sep 11 '13 at 13:28
terdonterdon
41.5k887136
Yes, I'm running on 12 cores. That does reduce the % levels that it reaches intopsuch that the average value is below that ofps, so that may be the difference. The process is a lot less active now, though, so it's hard to say...
– TTT
Sep 11 '13 at 15:48
1
@TTT this is a classic issue, it used to drive me up the wall before I discovered the shift+I thing.
– terdon
Sep 11 '13 at 17:18
add a comment |
This question is old, but in my opinion the answer is incorrect. ps and top calculates CPU usage using different methods.
from man top:
- %CPU -- CPU Usage
The task's share of the elapsed CPU time since the last screen update, expressed as a percentage of total CPU time.
from man ps:
CPU usage is currently expressed as the percentage of time spent
running during the entire lifetime of a process.
So, lets say you have a process that was started a week ago and during that time it used 2.2% of CPU time on average. If suddenly it would became CPU intensive ( constantly consuming 100%) - looking at ps you would observe same 2.2% for the first few hours.
answered Jan 2 at 21:12
trukttrukt
211
You're half-right in this case, sincemauiruns continuously in the background. But, even ifpsandtopaveraged over the same time period, there'd still be a 12x difference because of the issue noted by the accepted answer. So, both answers are partially correct.
– TTT
Jan 12 at 15:25
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
The likeliest reason is that top shows the percentage values as a percentage of a single CPU while ps shows the percentage of total available CPU power. Try running top and hitting ShiftI while it's running to show the percentage of all cores.
If this is a server cluster with a lot of CPUs, what you describe is normal behavior. Also see here.
edited Mar 20 '17 at 10:16
Community♦
1
answered Sep 11 '13 at 13:28
terdonterdon
41.5k887136
Yes, I'm running on 12 cores. That does reduce the % levels that it reaches intopsuch that the average value is below that ofps, so that may be the difference. The process is a lot less active now, though, so it's hard to say...
– TTT
Sep 11 '13 at 15:48
1
@TTT this is a classic issue, it used to drive me up the wall before I discovered the shift+I thing.
– terdon
Sep 11 '13 at 17:18
add a comment |
The likeliest reason is that top shows the percentage values as a percentage of a single CPU while ps shows the percentage of total available CPU power. Try running top and hitting ShiftI while it's running to show the percentage of all cores.
If this is a server cluster with a lot of CPUs, what you describe is normal behavior. Also see here.
edited Mar 20 '17 at 10:16
Community♦
1
answered Sep 11 '13 at 13:28
terdonterdon
41.5k887136
Yes, I'm running on 12 cores. That does reduce the % levels that it reaches intopsuch that the average value is below that ofps, so that may be the difference. The process is a lot less active now, though, so it's hard to say...
– TTT
Sep 11 '13 at 15:48
1
@TTT this is a classic issue, it used to drive me up the wall before I discovered the shift+I thing.
– terdon
Sep 11 '13 at 17:18
add a comment |
The likeliest reason is that top shows the percentage values as a percentage of a single CPU while ps shows the percentage of total available CPU power. Try running top and hitting ShiftI while it's running to show the percentage of all cores.
If this is a server cluster with a lot of CPUs, what you describe is normal behavior. Also see here.
edited Mar 20 '17 at 10:16
Community♦
1
answered Sep 11 '13 at 13:28
terdonterdon
41.5k887136
The likeliest reason is that top shows the percentage values as a percentage of a single CPU while ps shows the percentage of total available CPU power. Try running top and hitting ShiftI while it's running to show the percentage of all cores.
If this is a server cluster with a lot of CPUs, what you describe is normal behavior. Also see here.
edited Mar 20 '17 at 10:16
Community♦
1
answered Sep 11 '13 at 13:28
terdonterdon
41.5k887136
edited Mar 20 '17 at 10:16
Community♦
1
edited Mar 20 '17 at 10:16
Community♦
1
edited Mar 20 '17 at 10:16
Community♦
1
1
answered Sep 11 '13 at 13:28
terdonterdon
41.5k887136
answered Sep 11 '13 at 13:28
terdonterdon
41.5k887136
answered Sep 11 '13 at 13:28
terdonterdon
41.5k887136
41.5k887136
Yes, I'm running on 12 cores. That does reduce the % levels that it reaches intopsuch that the average value is below that ofps, so that may be the difference. The process is a lot less active now, though, so it's hard to say...
– TTT
Sep 11 '13 at 15:48
1
@TTT this is a classic issue, it used to drive me up the wall before I discovered the shift+I thing.
– terdon
Sep 11 '13 at 17:18
add a comment |
Yes, I'm running on 12 cores. That does reduce the % levels that it reaches intopsuch that the average value is below that ofps, so that may be the difference. The process is a lot less active now, though, so it's hard to say...
– TTT
Sep 11 '13 at 15:48
1
@TTT this is a classic issue, it used to drive me up the wall before I discovered the shift+I thing.
– terdon
Sep 11 '13 at 17:18
Yes, I'm running on 12 cores. That does reduce the % levels that it reaches in
top such that the average value is below that of ps, so that may be the difference. The process is a lot less active now, though, so it's hard to say...– TTT
Sep 11 '13 at 15:48
Yes, I'm running on 12 cores. That does reduce the % levels that it reaches in
top such that the average value is below that of ps, so that may be the difference. The process is a lot less active now, though, so it's hard to say...– TTT
Sep 11 '13 at 15:48
1
1
@TTT this is a classic issue, it used to drive me up the wall before I discovered the shift+I thing.
– terdon
Sep 11 '13 at 17:18
@TTT this is a classic issue, it used to drive me up the wall before I discovered the shift+I thing.
– terdon
Sep 11 '13 at 17:18
add a comment |
This question is old, but in my opinion the answer is incorrect. ps and top calculates CPU usage using different methods.
from man top:
- %CPU -- CPU Usage
The task's share of the elapsed CPU time since the last screen update, expressed as a percentage of total CPU time.
from man ps:
CPU usage is currently expressed as the percentage of time spent
running during the entire lifetime of a process.
So, lets say you have a process that was started a week ago and during that time it used 2.2% of CPU time on average. If suddenly it would became CPU intensive ( constantly consuming 100%) - looking at ps you would observe same 2.2% for the first few hours.
answered Jan 2 at 21:12
trukttrukt
211
You're half-right in this case, sincemauiruns continuously in the background. But, even ifpsandtopaveraged over the same time period, there'd still be a 12x difference because of the issue noted by the accepted answer. So, both answers are partially correct.
– TTT
Jan 12 at 15:25
add a comment |
This question is old, but in my opinion the answer is incorrect. ps and top calculates CPU usage using different methods.
from man top:
- %CPU -- CPU Usage
The task's share of the elapsed CPU time since the last screen update, expressed as a percentage of total CPU time.
from man ps:
CPU usage is currently expressed as the percentage of time spent
running during the entire lifetime of a process.
So, lets say you have a process that was started a week ago and during that time it used 2.2% of CPU time on average. If suddenly it would became CPU intensive ( constantly consuming 100%) - looking at ps you would observe same 2.2% for the first few hours.
answered Jan 2 at 21:12
trukttrukt
211
You're half-right in this case, sincemauiruns continuously in the background. But, even ifpsandtopaveraged over the same time period, there'd still be a 12x difference because of the issue noted by the accepted answer. So, both answers are partially correct.
– TTT
Jan 12 at 15:25
add a comment |
This question is old, but in my opinion the answer is incorrect. ps and top calculates CPU usage using different methods.
from man top:
- %CPU -- CPU Usage
The task's share of the elapsed CPU time since the last screen update, expressed as a percentage of total CPU time.
from man ps:
CPU usage is currently expressed as the percentage of time spent
running during the entire lifetime of a process.
So, lets say you have a process that was started a week ago and during that time it used 2.2% of CPU time on average. If suddenly it would became CPU intensive ( constantly consuming 100%) - looking at ps you would observe same 2.2% for the first few hours.
answered Jan 2 at 21:12
trukttrukt
211
This question is old, but in my opinion the answer is incorrect. ps and top calculates CPU usage using different methods.
from man top:
- %CPU -- CPU Usage
The task's share of the elapsed CPU time since the last screen update, expressed as a percentage of total CPU time.
from man ps:
CPU usage is currently expressed as the percentage of time spent
running during the entire lifetime of a process.
So, lets say you have a process that was started a week ago and during that time it used 2.2% of CPU time on average. If suddenly it would became CPU intensive ( constantly consuming 100%) - looking at ps you would observe same 2.2% for the first few hours.
answered Jan 2 at 21:12
trukttrukt
211
answered Jan 2 at 21:12
trukttrukt
211
answered Jan 2 at 21:12
trukttrukt
211
answered Jan 2 at 21:12
trukttrukt
211
211
You're half-right in this case, sincemauiruns continuously in the background. But, even ifpsandtopaveraged over the same time period, there'd still be a 12x difference because of the issue noted by the accepted answer. So, both answers are partially correct.
– TTT
Jan 12 at 15:25
add a comment |
You're half-right in this case, sincemauiruns continuously in the background. But, even ifpsandtopaveraged over the same time period, there'd still be a 12x difference because of the issue noted by the accepted answer. So, both answers are partially correct.
– TTT
Jan 12 at 15:25
You're half-right in this case, since
maui runs continuously in the background. But, even if ps and top averaged over the same time period, there'd still be a 12x difference because of the issue noted by the accepted answer. So, both answers are partially correct.– TTT
Jan 12 at 15:25
You're half-right in this case, since
maui runs continuously in the background. But, even if ps and top averaged over the same time period, there'd still be a 12x difference because of the issue noted by the accepted answer. So, both answers are partially correct.– TTT
Jan 12 at 15:25
add a comment |
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You mean
psnever ever changes and is always 2.2? Could you post the output ofpsandtopfor the command in question so we can have a look?– terdon
Sep 10 '13 at 13:18
@terdon I updated the original post with additional information.
– TTT
Sep 11 '13 at 13:16