[libvirt PATCH] Revert "qemuDomainSetNumaParamsLive: set nodeset for root cgroup"

[Michal Prívozník]

On 5/21/21 3:40 PM, Pavel Hrdina wrote:
> This reverts commit <1b22dd6dd44202094e0f78f887cbe790c00e9ebc>.
> 
> First of all, the reverted commit is incomplete. It only sets
> cpuset.mems in the VM root cgroup when the API is used but there is no
> code that would do the same when the VM is started.
> 
> Libvirt never places any process into the VM root cgroup directly. All
> the supporting processes like slirp-helper or dbus-daemon are placed
> into the emulator sub-cgroup and all the QEMU threads are distributed
> between emulator, vcpu* and iothread* sub-cgroups. The scenario
> described in the reverted commit can happen only if someone manually
> adds any process there which we should not care about.
> 
> If we would like to set the limit in the VM root cgroup we need to
> introduce better logic:
> 
>     - set both (old and new) numa group in the VM root cgroup
>     - change the numa group in all sub-cgroups to new value
>     - finally set only the new value in the VM root cgroup
> 
> The simplest fix now is to revert the commit.
> 
> Signed-off-by: Pavel Hrdina <phrdina at redhat.com>
> ---
>  src/qemu/qemu_driver.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index e10e699a1a..a972662c3f 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -8797,10 +8797,6 @@ qemuDomainSetNumaParamsLive(virDomainObj *vm,
>              return -1;
>      }
>  
> -    /* set nodeset for root cgroup */
> -    if (virCgroupSetCpusetMems(priv->cgroup, nodeset_str) < 0)
> -        return -1;
> -
>      return 0;
>  }
>  
> 

Ooops O:-)

Reviewed-by: Michal Privoznik <mprivozn at redhat.com>

Michal