VirtualBox

Opened 15 years ago

Closed 9 years ago

#3779 closed enhancement (obsolete)

100% cpu load on host with 1000hz guest kernels

Reported by: Niki Waibel Owned by:
Component: other Version: VirtualBox 2.2.0
Keywords: cpu load Cc:
Guest type: other Host type: other

Description (last modified by Frank Mehnert)

yes, the manual says:

11.3 Linux guests
11.3.1 Linux guests may cause a high CPU load
Some Linux guests may cause a high CPU load even if the guest system appears to
be idle. This can be caused by a high timer frequency of the guest kernel. Some
Linux distributions, for example Fedora, ship a Linux kernel configured for a timer
frequency of 1000Hz. We recommend to recompile the guest kernel and to select a
timer frequency of 100Hz.

but i'd like to request an enhancement to fix this.

sure, using a 100hz guest kernel helps, reducing the load on the host. but running 10 100hz guest kernels will give the same problem.

further, running 1000hz kernels on other virtualisation sw works just smoothly. this means, with some effort, it is possible to fix this issue.

Change History (7)

comment:1 by Sander van Leeuwen, 15 years ago

priority: majorminor

Did you try running 10 100hz guests? I don't see any reason why that should cause a problem.

Also running a 1000 hz guest should be fine if the host timer resolution matches.

in reply to:  1 comment:2 by Niki Waibel, 15 years ago

yes, 10 100hz guests cause the host system to be idle around 60%. the 10 VirtualBox processes use between 1 and 10%cpu, and spread around the 2 cores of the host.

1 1000Hz guest cause the host system to be idle around 55%. the VirtualBox process use around 43% cpu.

100hz guests: dsl-4.4.10, linux-2.4.31

1000hz guest: centos-5.3, linux-2.6.18-128.1.10.el5.centos.plus

host: CONFIG_NO_HZ=y CONFIG_HZ_300=y CONFIG_HZ=300 linux-2.6.29.1, 2x Intel(R) Core(TM)2 Duo CPU T7300 @ 2.00GHz scaling_governor: performance

the only solution right now is to use an old 100hz centos vm-kernel, distributed on http://people.centos.org/tru/kernel-vm

comment:3 by Niki Waibel, 15 years ago

same situation with 3.0.2.

comment:4 by Niki Waibel, 15 years ago

same for 3.0.4

comment:5 by Technologov, 14 years ago

The problem still exists for VBox 3.2.6, and I don't know if this is 'fixable' or not. Especially true for SMP guests, where guest's keyboard makes several presses on each real (host keyboard's) key press (RHEL5 guest with 16 vCPUs).

My recommendation: Boot Linux guests with "divider=10". This will slow down their clocks from 1000Hz to 100Hz.

-Technologov

comment:6 by Technologov, 14 years ago

A possible idea: VBoxLinuxAdditions could detect the high frequency timer in (Red Hat) Linux guests, and add "divider=10" to the GRUB config file.

This looks like a reasonable middle ground, where this solution will work for 90%+ of the users, without requiring them deep Linux skills and kernel recompilations.

-Technologov

comment:7 by Frank Mehnert, 9 years ago

Description: modified (diff)
Resolution: obsolete
Status: newclosed
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