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List:       libvir-list
Subject:    Re: [PATCH Libvirt 06/11] qemu_driver: Extend qemuDomainGetVcpus
From:       Peter Krempa <pkrempa () redhat ! com>
Date:       2023-07-31 7:13:31
Message-ID: ZMdfGwnn9V6E6650 () angien ! pipo ! sk
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On Sat, Aug 13, 2022 at 11:06:27 +0800, ~hyman wrote:
> From: Hyman Huang(黄勇) <yong.huang@smartx.com>
> 
> Extend qemuDomainGetVcpus for getting dirty page rate upper
> limit info so 'virsh vcpuinfo' api can display it.
> 
> Signed-off-by: Hyman Huang(黄勇) <yong.huang@smartx.com>
> ---
>  include/libvirt/libvirt-domain.h |  2 ++
>  src/qemu/qemu_driver.c           | 55 ++++++++++++++++++++++++++++++++
>  2 files changed, 57 insertions(+)
> 
> diff --git a/include/libvirt/libvirt-domain.h b/include/libvirt/libvirt-domain.h
> index df7deffaa9..4c63d0be7c 100644
> --- a/include/libvirt/libvirt-domain.h
> +++ b/include/libvirt/libvirt-domain.h
> @@ -2395,6 +2395,8 @@ struct _virVcpuInfo {
>      int state;                  /* value from virVcpuState */
>      unsigned long long cpuTime; /* CPU time used, in nanoseconds */
>      int cpu;                    /* real CPU number, or one of the values from virVcpuHostCpuState */
> +    unsigned long long limit;   /* virtual cpu dirty page rate upper limit in MB/s */
> +    unsigned long long current; /* current virtual cpu dirty page rate in MB/s */
>  };

Adding fields to C structs makes them ABI (binary) incompatible with
programs compiled with libvirt before this change. Same goes for the RPC
protocol.

Thus we must never add to existing structs.

I suggest you use the bulk stats API
(virConnectGetAllDomainStats/virDomainListGetStats)
which is extensible.

NACK to this patch.

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