groundsea
Enthusiast
Enthusiast

The question about CPU allocation in reservation pool of OrgVDC

Hi experts,

I have a question about CPU allocation in reservation pool of OrgVDC.

I want to know if the configured CPU allcation value is only correlation with the vCPU of the vAPP in the reservation pool OrgVDC?

For example, I have a vApp which has 6 vCPU in the reservation pool OrgVDC. This vApp has multiple vmxnet3 vnics, and is used for packets forwarding,

so it will consume additional system CPU to assist the vnics to receive and transimit packets.

Does this consumed system CPU be accumulated to the CPU allocation of the reservation pool?

Or only the 6 vCPUs of vApp were accumulated to the CPU allocation?

Thank you very much!

BR.

Haifeng.

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2 Replies
Sreec
VMware Employee
VMware Employee

When you create reservation pool you would have entered -> Enter the maximum amount of CPU, in GHz, to allocate to virtual machines running in the organization vDC which is the key CPU matrix for reservation pool VDC Vapps(VM's) . Behind the scene what happens is the allocated CPU is immediately taken out from PvDC and that resource is no more available for other VDC's and if needed we can set VM level reservation as well. What is tbeing reserved (since the model is reservation pool) VM will use the same set of resources unless we manually go and change the reservations. Irrespective of the packet flow pattern (Ingress/Egress) , what is being reserved is the only resource for VM .

In general below points are considered for network performance from hardware perspective.

  • Checksum offload
  • TCP segmentation offload (TSO)
  • Ability to handle high-memory DMA (that is, 64-bit DMA addresses)
  • Ability to handle multiple Scatter Gather elements per Tx frame
  • Jumbo frames (JF)
  • Large receive offload (LRO)
  • When using a virtualization encapsulation protocol, such as VXLAN or GENEVE, the NICs should support offload of that protocol’s encapsulated packets.
  • Receive Side Scaling (RSS)
Cheers,
Sree | CKA|CKAD|VCIX-3X| VCAP-4X| VExpert 5x
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groundsea
Enthusiast
Enthusiast

Hi Sree,

Thank you for your response. Your statement is quite correct I think.

But I'm still confused about whether the system CPU will be accumulated to the VDC or VM's reservation value or not?

suppose I have an intel CPU , 2.5GHz per core,  and I create a reservation pool with the CPU reservation 10G Hz(which means 4 physical cores).

Then I create a VM in the vDC with 4 vCPU and reservation value is 10G Hz too.

Then this VM begin to transmit and receive packets at its full speed. I have added the addvanced parameter ctxPerDev=1 to each vmxnet3 vnic of the VM,

so the ESXi will assgin multiple threads to assist the VM to transmit the packets. and ESXi also has other assistant threads to receive packets.

If these assistant threads consumed CPU is accumulated to the reservation value(10G Hz), then the vCPU in the VM can't obtain the full 10GHz.

I just want to make it clarify.

Thank you very much!

BR.

Haifeng.

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