| CPU limiting [message #41226] |
Wed, 15 December 2010 09:43  |
Woet
Messages: 9
Registered: November 2008
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Junior Member |
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Using the latest RHEL5, CPU limiting is not working as it should. While it does limit the CPU in the VPS (e.g. causing a load of 20), it also raises the load on the hostnode, basically rendering it useless.
Test case below: check the load, create a VPS, make it spawn a lot of infinite loops, check load again, stop the VPS, check load again.
Expected result: the load on the host node to go up with maximum 1, since I limited the VPS to 100% of one CPU.
Actual result: load on the host node rises way beyond the limits set.
kitten:~# vzctl create 2000 --ostemplate=debian-5.0-x86
Creating container private area (debian-5.0-x86)
Performing postcreate actions
Container private area was created
kitten:~# vzctl set 2000 --cpus 1 --save
Saved parameters for CT 2000
kitten:~# vzctl set 2000 --cpulimit 100 --save
Saved parameters for CT 2000
kitten:~# uptime
10:37:04 up 30 days, 2:36, 2 users, load average: 4.29, 3.41, 2.71
kitten:~# vzctl start 2000
Starting container ...
Container is mounted
Setting CPU limit: 100
Setting CPU units: 1000
Setting CPUs: 1
Container start in progress...
kitten:~# vzctl enter 2000
entered into CT 2000
kitten:/# uptime
12:37:12 up 0 min, 0 users, load average: 0.08, 0.02, 0.01
kitten:/# while true; do true; done &
[1] 15736
kitten:/# while true; do true; done &
[2] 15853
kitten:/# while true; do true; done &
[3] 15854
kitten:/# while true; do true; done &
[4] 15855
kitten:/# while true; do true; done &
[5] 15910
kitten:/# while true; do true; done &
[6] 18398
kitten:/# while true; do true; done &
[7] 18417
kitten:/# while true; do true; done &
[8] 18418
kitten:/# while true; do true; done &
[9] 18431
kitten:/# while true; do true; done &
[10] 19801
kitten:/# while true; do true; done &
[11] 19804
kitten:/# while true; do true; done &
[12] 19807
kitten:/# while true; do true; done &
[13] 19820
kitten:/# while true; do true; done &
[14] 19862
kitten:/# while true; do true; done &
[15] 19896
kitten:/# while true; do true; done &
[16] 19934
kitten:/# while true; do true; done &
[17] 19935
kitten:/# while true; do true; done &
[18] 20380
kitten:/# while true; do true; done &
[19] 20432
kitten:/# while true; do true; done &
[20] 20433
kitten:/# while true; do true; done &
[21] 20436
kitten:/# while true; do true; done &
[22] 20437
kitten:/# while true; do true; done &
[23] 20440
kitten:/# while true; do true; done &
[24] 20441
kitten:/# while true; do true; done &
[25] 21595
kitten:/# while true; do true; done &
kitten:/# uptime
12:38:04 up 0 min, 0 users, load average: 4.67, 1.13, 0.37
kitten:/# uptime
12:38:19 up 1 min, 0 users, load average: 9.17, 2.30, 0.77
kitten:/# uptime
12:38:21 up 1 min, 0 users, load average: 10.44, 2.67, 0.90
kitten:/# uptime
12:38:23 up 1 min, 0 users, load average: 10.44, 2.67, 0.90
kitten:/# exit
logout
exited from CT 2000
kitten:~# uptime
10:38:26 up 30 days, 2:37, 1 user, load average: 13.71, 6.00, 3.64
kitten:~# vzctl stop 2000
Stopping container ...
Container was stopped
Container is unmounted
kitten:~# uptime
10:39:01 up 30 days, 2:38, 1 user, load average: 15.25, 7.38, 4.20
kitten:~# uptime
10:39:26 up 30 days, 2:38, 1 user, load average: 10.85, 6.98, 4.15
kitten:~# uptime
10:40:13 up 30 days, 2:39, 1 user, load average: 6.13, 6.28, 4.04
kitten:~# uptime
10:40:28 up 30 days, 2:39, 1 user, load average: 4.90, 6.00, 3.99
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| Re: CPU limiting [message #41320 is a reply to message #41319] |
Thu, 30 December 2010 09:58  |
Woet
Messages: 9
Registered: November 2008
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Junior Member |
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Please refer to this topic too:
ht tp://forum.openvz.org/index.php?t=msg&goto=21013&
Quote:
If a VE has a very low cpulimit, it can have a high load despite low amounts of work being done (high amount of idle cpu %). Due to this, the HN load can be very deceiving.
For example- take a VE, set cpulimit to 2, start it, and run 100 cpuburn processes inside. now look at you HN's load and also the idle/user cpu %. you will see the cpus are doing almost nothing yet the load is around 100.
This should be fixed so the load average is correct at all times.
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