[libvirt-users] What global_quota option mean? What's its logic?
Hi techs, Could you please explain or refer me to documentation where I could find a description of global_quota schedinfo option. Someone told me that it could mean a cpu limitation in percents like: global_quota : 25000 (does it mean cpu limit % set to 25 ?) Is it true? What other parameters mean in below output? I didn't find any related documentation at libvirt.org. Could you help me to describe me or refer to some description what below schedinfo options mean? Thanks. [root@cpkvm ~]# virsh list Id Name State ---------------------------------------------------- 3 kvmtestvm running [root@cpkvm ~]# virsh schedinfo 3 Scheduler : posix cpu_shares : 154 vcpu_period : 100000 vcpu_quota : -1 emulator_period: 100000 emulator_quota : -1 global_period : 100000 global_quota : -1 iothread_period: 100000 iothread_quota : -1 [root@cpkvm ~]# virsh schedinfo 3 --set global_quota=25 Scheduler : posix error: invalid argument: value of 'global_quota' is out of range [1000, 18446744073709551] [1000, 18446744073709551] - what this range mean? [root@cpkvm ~]# [root@cpkvm ~]# virsh schedinfo 3 --set global_quota=25000 Scheduler : posix cpu_shares : 154 vcpu_period : 100000 vcpu_quota : 12500 emulator_period: 100000 emulator_quota : -1 global_period : 100000 global_quota : 25000 iothread_period: 100000 iothread_quota : 25000 [root@cpkvm ~]#
On Thu, Nov 02, 2017 at 03:03:56PM +0200, Volo M. wrote:
Hi techs,
Could you please explain or refer me to documentation where I could find a description of global_quota schedinfo option. Someone told me that it could mean a cpu limitation in percents like: global_quota : 25000 (does it mean cpu limit % set to 25 ?)
The _quota values are relative to the _period, both in milliseconds and refer to the cumulative CPU time available to all the processes/threads in a group. See the documentation in the kernel: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Docu... So with global_period being set to 100000, a value of 25000 would mean that all the threads of the virtual machine would be limited to use at most 25 % of 1 CPU.
Is it true? What other parameters mean in below output? I didn't find any related documentation at libvirt.org. Could you help me to describe me or refer to some description what below schedinfo options mean? Thanks.
[...]
[root@cpkvm ~]# virsh schedinfo 3 --set global_quota=25
Scheduler : posix
error: invalid argument: value of 'global_quota' is out of range [1000, 18446744073709551]
[1000, 18446744073709551] - what this range mean?
These are the minimum and maximum values that were accepted by the kernel at the time when this error message was implemented in libvirt. Jan
Very interesting! I did this configuration and I can see my core working just in 25%. I would like to try the same with memory.....I am looking for that. Thanks. 2017-11-02 13:58 GMT-02:00 Ján Tomko <jtomko@redhat.com>:
On Thu, Nov 02, 2017 at 03:03:56PM +0200, Volo M. wrote:
Hi techs,
Could you please explain or refer me to documentation where I could find a description of global_quota schedinfo option. Someone told me that it could mean a cpu limitation in percents like: global_quota : 25000 (does it mean cpu limit % set to 25 ?)
The _quota values are relative to the _period, both in milliseconds and refer to the cumulative CPU time available to all the processes/threads in a group.
See the documentation in the kernel: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin ux.git/tree/Documentation/scheduler/sched-bwc.txt
So with global_period being set to 100000, a value of 25000 would mean that all the threads of the virtual machine would be limited to use at most 25 % of 1 CPU.
Is it true?
What other parameters mean in below output? I didn't find any related documentation at libvirt.org. Could you help me to describe me or refer to some description what below schedinfo options mean? Thanks.
[...]
[root@cpkvm ~]# virsh schedinfo 3 --set global_quota=25
Scheduler : posix
error: invalid argument: value of 'global_quota' is out of range [1000, 18446744073709551]
[1000, 18446744073709551] - what this range mean?
These are the minimum and maximum values that were accepted by the kernel at the time when this error message was implemented in libvirt.
Jan
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participants (3)
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Ján Tomko -
Thiago Oliveira -
Volo M.