High CPU Usage , users affected Post: 302887021

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Operating Systems AIX High CPU Usage , users affected Post 302887021 by rbatte1 on Wednesday 5th of February 2014 06:06:47 AM

02-05-2014

Moderator

So, this is a partitioned server. It has an allocation of 1.3 CPUs. I'm assuming therefore that there are other partitions defined, and perhaps a little spare CPU on the chassis as a whole. If the partition is capped, then it will use up to 1.3 CPUs and no more. If it is uncapped and there is spare CPU then it will burst through the limit and you will see the value for entitled CPU on sar or vmstat exceeding 100%.

If you take the cap off the partition and other servers are busy, they will be guaranteed to get their allocated CPU as a minimum, however as already pointed out by Zaxxon, you are not CPU bound (95% entitled capacity)

Consider partitions:-

1.3 CPU shared
3.0 CPU shared
2.0 CPU dedicated
1.7 CPU shared

Server has 8 CPUs. Two are dedicated, so out of the reckoning. If the shared CPU partitions are all uncapped, then if the other two are idle, the busy one could get 6 CPUs. If all are busy, then they will be limited as shown. If partition 4 is idle and 1 & 2 are busy then they will compete for the spare CPU (after both have reached their entitled CPU limit) and you can weight them to show a preference.

You may be better just upping your CPU allocation a little then re-activating the partition (not just a reboot) else your end user will get used to having the full spare CPU available and then complain when it's in use elsewhere on the chassis. Is there another partition you could squeeze down, but take the cap off because it is rarely busy?

We have our set as 0.1 CPU, production uncapped, test/dev capped.

I hope that this helps.

Robin
Liverpool/Blackburn
UK

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chcpu

CHCPU(8)						       System Administration							  CHCPU(8)

NAME

       chcpu - configure CPUs

SYNOPSIS

       chcpu -c|-d|-e|-g cpu-list
       chcpu -p mode
       chcpu -r|-h|-V

DESCRIPTION

       chcpu  can  modify  the state of CPUs.  It can enable or disable CPUs, scan for new CPUs, change the CPU dispatching mode of the underlying
       hypervisor, and request CPUs from the hypervisor (configure) or return CPUs to the hypervisor (deconfigure).

       Some options have a cpu-list argument.  Use this argument to specify a comma-separated list of CPUs.  The list can contain  individual  CPU
       addresses  or ranges of addresses.  For example, 0,5,7,9-11 makes the command applicable to the CPUs with the addresses 0, 5, 7, 9, 10, and
       11.

OPTIONS

       -c, --configure cpu-list
	      Configure the specified CPUs.  Configuring a CPU means that the hypervisor takes a CPU from the CPU pool and assigns it to the  vir-
	      tual hardware on which your kernel runs.

       -d, --disable cpu-list
	      Disable the specified CPUs.  Disabling a CPU means that the kernel sets it offline.

       -e, --enable cpu-list
	      Enable the specified CPUs.  Enabling a CPU means that the kernel sets it online.	A CPU must be configured, see -c, before it can be
	      enabled.

       -g, --deconfigure cpu-list
	      Deconfigure the specified CPUs.  Deconfiguring a CPU means that the hypervisor removes the CPU from the virtual  hardware  on  which
	      the Linux instance runs and returns it to the CPU pool.  A CPU must be offline, see -d, before it can be deconfigured.

       -p, --dispatch mode
	      Set  the	CPU  dispatching mode (polarization).  This option has an effect only if your hardware architecture and hypervisor support
	      CPU polarization.  Available modes are:

		     horizontal  The workload is spread across all available CPUs.
		     vertical	 The workload is concentrated on few CPUs.

       -r, --rescan
	      Trigger a rescan of CPUs.  After a rescan, the Linux kernel recognizes the new CPUs.  Use this option on systems that do	not  auto-
	      matically detect newly attached CPUs.

       -V, --version
	      Display version information and exit.

       -h, --help
	      Display help text and exit.

RETURN CODES

       chcpu has the following return codes:

       0      success

       1      failure

       64     partial success

AUTHOR

       Heiko Carstens <heiko.carstens@de.ibm.com>

COPYRIGHT

       Copyright IBM Corp. 2011

SEE ALSO

       lscpu(1)

AVAILABILITY

       The  chcpu  command  is	part  of the util-linux package and is available from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils
       /util-linux/>.

util-linux							     July 2014								  CHCPU(8)