Public bug reported:
It was brought to my attention that:
In a PowerPC based server, PERF seems to acuse cpu-migrations when only
a single cpu is activated.
## perf
Performance counter stats for 'CPU(s) 0':
15027.888988 task-clock (msec) # 1.000 CPUs utilized
[100.00%]
25,206 context-switches # 0.002 M/sec
[100.00%]
3,518 cpu-migrations # 0.234 K/sec
[100.00%]
639 page-faults # 0.043
K/sec
41,545,780,384 cycles # 2.765 GHz
[66.68%]
2,868,753,319 stalled-cycles-frontend # 6.91% frontend cycles idle
[50.01%]
30,162,193,535 stalled-cycles-backend # 72.60% backend cycles idle
[50.01%]
11,161,722,533 instructions # 0.27 insns per
cycle
# 2.70 stalled cycles per insn [66.68%]
1,544,072,679 branches # 102.747 M/sec
[49.99%]
52,536,867 branch-misses # 3.40% of all
branches [49.99%]
15.027768835 seconds time elapsed
## lscpu
Architecture: ppc64le
Byte Order: Little Endian
CPU(s): 128
On-line CPU(s) list: 0
Off-line CPU(s) list: 1-127
Thread(s) per core: 1
Core(s) per socket: 1
Socket(s): 1
NUMA node(s): 2
Model: 8335-GCA
L1d cache: 64K
L1i cache: 32K
L2 cache: 512K
L3 cache: 8192K
NUMA node0 CPU(s): 0
NUMA node8 CPU(s):
So either task migrations are being done to offline cpus or perf is
accounting it wrong.
** Affects: linux (Ubuntu)
Importance: Low
Assignee: Rafael David Tinoco (inaddy)
Status: Confirmed
** Changed in: linux (Ubuntu)
Status: New => Confirmed
** Changed in: linux (Ubuntu)
Importance: Undecided => Low
** Changed in: linux (Ubuntu)
Assignee: (unassigned) => Rafael David Tinoco (inaddy)
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https://bugs.launchpad.net/bugs/1575407
Title:
Trusty + 3.19 (lts-vivid) PERF wrong cpu-migration counter
Status in linux package in Ubuntu:
Confirmed
Bug description:
It was brought to my attention that:
In a PowerPC based server, PERF seems to acuse cpu-migrations when
only a single cpu is activated.
## perf
Performance counter stats for 'CPU(s) 0':
15027.888988 task-clock (msec) # 1.000 CPUs utilized
[100.00%]
25,206 context-switches # 0.002 M/sec
[100.00%]
3,518 cpu-migrations # 0.234
K/sec [100.00%]
639 page-faults #
0.043 K/sec
41,545,780,384 cycles # 2.765 GHz
[66.68%]
2,868,753,319 stalled-cycles-frontend # 6.91% frontend cycles
idle [50.01%]
30,162,193,535 stalled-cycles-backend # 72.60% backend cycles idle
[50.01%]
11,161,722,533 instructions # 0.27 insns per
cycle
# 2.70 stalled cycles per insn [66.68%]
1,544,072,679 branches # 102.747 M/sec
[49.99%]
52,536,867 branch-misses # 3.40% of all
branches [49.99%]
15.027768835 seconds time elapsed
## lscpu
Architecture: ppc64le
Byte Order: Little Endian
CPU(s): 128
On-line CPU(s) list: 0
Off-line CPU(s) list: 1-127
Thread(s) per core: 1
Core(s) per socket: 1
Socket(s): 1
NUMA node(s): 2
Model: 8335-GCA
L1d cache: 64K
L1i cache: 32K
L2 cache: 512K
L3 cache: 8192K
NUMA node0 CPU(s): 0
NUMA node8 CPU(s):
So either task migrations are being done to offline cpus or perf is
accounting it wrong.
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