New submission from Damian Myerscough:
I have been running a simple script inside a Docker container to cause the
container to trigger oom-killer.
>>> mem = {}
>>> for i in range(65535):
... mem[i] = "A" * 65535
When oom-killer is trigger I see a large number of involuntary context switches
and major page faults which causes a spike in CPU
and disk.
# /usr/bin/time --verbose python
Python 2.7.9 (default, Mar 1 2015, 12:57:24)
[GCC 4.9.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> mem = {}
>>> for i in range(65535):
... mem[i] = "A" * 65535
...
Command terminated by signal 9
Command being timed: "python"
User time (seconds): 0.13
System time (seconds): 3.83
Percent of CPU this job got: 17%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:22.94
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 2096516
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 33536
Minor (reclaiming a frame) page faults: 524545
Voluntary context switches: 30706
Involuntary context switches: 137852
Swaps: 0
File system inputs: 8499072
File system outputs: 0
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0
I tried the same test using NodeJS/C++ and I could see a lot less involuntary
context switches and major page faults which indicates this could
be a Python issue.
# /usr/bin/time --verbose ./alloc_forever 1024 5 524288000
initial_alloc_amount: 1024, sleep_duration: 5, alloc_amount: 524288000
memory: 501.07MB
memory: 1001.29MB
memory: 1501.19MB
memory: 2001.09MB
Command terminated by signal 9
Command being timed: "./alloc_forever 1024 5 524288000"
User time (seconds): 0.63
System time (seconds): 0.97
Percent of CPU this job got: 7%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:21.61
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 2096536
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 11
Minor (reclaiming a frame) page faults: 524178
Voluntary context switches: 17
Involuntary context switches: 284
Swaps: 0
File system inputs: 336
File system outputs: 0
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0
--
messages: 261781
nosy: DamianMyerscough
priority: normal
severity: normal
status: open
title: Large Involuntary context switches during oom-killer
type: resource usage
versions: Python 2.7, Python 3.2, Python 3.3, Python 3.4, Python 3.5
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<http://bugs.python.org/issue26562>
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