Applying CPU Limits

2008-12-27T01:02:39Z

SilvioRhatto: Initial version

= Applying CPU limits =

This is a short summary on how to apply limits. This doesn't cover how to choose the values but just on how to apply the numbers in a running vserver without saving the configuration.

== Kernel config ==

First check whether the kernel is with '''CONFIG_VSERVER_HARDCPU''' enabled:

# cat /boot/config-blah | grep CONFIG_VSERVER_HARDCPU
CONFIG_VSERVER_HARDCPU=y

== Context flag ==

Then check if the vserver you want to apply limits has the [http://linux-vserver.org/Capabilities_and_Flags#Context_flags_.28cflags.29 sched_hard] context flag enabled by checking the contents of ''/proc/virtual/<xid>/status''. The sched_hard flag is ''0x00000100'', so you have to find this value summed up in the vserver flag (see [http://www.mail-archive.com/vserver@list.linux-vserver.org/msg10448.html this message] for details). If its not enabled, use the following command (more info [http://www.mail-archive.com/vserver@list.linux-vserver.org/msg08385.html here]):

vattribute --set --xid <xid> --flag sched_hard

== Setting the limits ==

Then you should be able to set the limits with a command like this one (more info [http://oldwiki.linux-vserver.org/vsched+explained here]):

vsched --xid <xid> --fill-rate <fill-rate> --interval <interval> \
--fill-rate2 <fill-rate2> --interval2 <interval2> \
--tokens-max <tokens-max> --tokens-min <tokens-min> --idle-time --force

it's important to use the option ''--force'' so the limit is applied at the same time in the cpus. If you want to enable fair share (i.e, idle-time) for the vserver, make sure to use the ''--idle-time'' option at the previous command.

Then you should check at ''/proc/virtual/<xid>/sched'' (more info [http://linux-vserver.org/ProcFS#sched here]). Try a command like

watch -n1 cat /proc/virtual/<xid>/sched

If the collum "Ticks spent on hold" is greater than zero and the flag "On hold (H) or running (R)" assumes the hold value, then its working :)

If you want to remove the scheduling, use the command

vattribute --set --xid <xid> --flag ~sched_hard

But remember that these instructions just cover setting limits in a running vserver. To save the values you choose please refer to the [http://www.nongnu.org/util-vserver/doc/conf/configuration.html great flower page].

Documentation

2008-12-27T00:51:07Z

SilvioRhatto: Added link "Applying CPU Limits"

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Applying CPU Limits

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