[PATCH Libvirt v3 02/10] conf: Introduce XML for dirty limit configuration
Daniel P. Berrangé
berrange at redhat.com
Wed Sep 6 08:48:08 UTC 2023
On Tue, Aug 01, 2023 at 05:31:12PM +0800, ~hyman wrote:
> From: Hyman Huang(黄勇) <yong.huang at smartx.com>
>
> The upper limit (megabyte/s) of the dirty page rate configured
> by the user can be tracked by the XML. To allow this, add the
> following XML:
>
> <domain>
> ...
> <vcpu current='2'>3</vcpu>
> <vcpus>
> <vcpu id='0' hotpluggable='no' dirty_limit='10' order='1'.../>
> <vcpu id='1' hotpluggable='yes' dirty_limit='10' order='2'.../>
> </vcpus>
> ...
>
> The "dirty_limit" attribute in "vcpu" sub-element within "vcpus"
> element allows to set an upper limit for the individual vCPU. The
> value can be set dynamically by limit-dirty-page-rate API.
>
> Note that the dirty limit feature is based on the dirty-ring
> feature, so it requires dirty-ring size configuration in XML.
>
> Signed-off-by: Hyman Huang(黄勇) <yong.huang at smartx.com>
> ---
> docs/formatdomain.rst | 7 ++++++-
> src/conf/domain_conf.c | 26 ++++++++++++++++++++++++
> src/conf/domain_conf.h | 8 ++++++++
> src/conf/domain_validate.c | 33 +++++++++++++++++++++++++++++++
> src/conf/schemas/domaincommon.rng | 5 +++++
> 5 files changed, 78 insertions(+), 1 deletion(-)
>
> diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
> index bc469e5f9f..337b7ec9cc 100644
> --- a/docs/formatdomain.rst
> +++ b/docs/formatdomain.rst
> @@ -715,6 +715,11 @@ CPU Allocation
> be enabled and non-hotpluggable. On PPC64 along with it vCPUs that are in the
> same core need to be enabled as well. All non-hotpluggable CPUs present at
> boot need to be grouped after vCPU 0. :since:`Since 2.2.0 (QEMU only)`
> + ``dirty_limit`` :since:`Since 9.7.0 (QEMU and KVM only)`
> + The optional attribute ``dirty_limit`` allows to set an upper limit (MB/s)
> + of the dirty page rate for the vCPU. User can change the upper limit value
> + dynamically by using ``limit-dirty-page-rate`` API. Require ``dirty-ring``
> + size configured.
What scenarios would you want to apply such a limit ?
Is there to admins for sensible values to use when
setting this limit ?
What is the impact on the guest if it hits the limit ?
Is the snigle vCPU blocked for the remainder of some
timeslice, or are all vCPUs blocked ?
Does it even make sense to control this with different
values per-VCPU as opposed to a single value for the VM
as a whole ?
With regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
More information about the libvir-list
mailing list