[Xen-devel] Question about network performance difference between dom0 and host

[zhangleiqiang <zhangleiqiang@xxxxxxxxx>]

 I have done some network performance testing under XEN, and found the result 
which is somehow strange:

   When testing between Hosts (Sender and receiver servers are both booting 
from kernel-default), running only one netperf process will be enough to reach 
the upper limit of NIC. However, when testing between Dom0s (Sender and 
receiver servers are both booting from kernel-xen), we must run more count of 
netperf process to reach the upper limit of NIC, running only one netperf 
process the throughout was low. The results using one netperf process are as 
follows:

         TCP 512    TCP 1460     TCP 4096    TCP 8500
Hosts:    9134.24    9444.84  9448.05      9447.58    (Mbs)
Dom0s:    2063.9    3018.95     6561.29         5008.17    (Mbs)

  The question is why one netperf process cannot reach the max throughout of 
NIC under Dom0 ? I know that Dom0 will have extra overhead when handling 
interrupt which must be handled by hypervisor first, but I think it is not the 
reason for it.

  The testing environment details are as follows:

   1. Hardware
       a. CPU: Intel(R) Xeon(R) CPU E5645 @ 2.40GHz, 2 CPU 6 Cores with Hyper 
Thread enabled
       b. NIC: Intel Corporation 82599EB 10-Gigabit SFI/SFP+ Network Connection 
(rev 01)
   2. Sofware:
       a. HostOS: SUSE SLES 11 SP3 (Kernel 3.0.76)
       b. NIC Driver: IXGBE 3.21.2 
       c. OVS: 2.1.3
       d. MTU: 1600
       e. Dom0：6U6G
   3. Networking Environment:
       a. All network flows are transmit/receive through OVS
       b. Sender server and receiver server are connected directly between 10GE 
NIC
   4. Testing Tools:
       a. Sender: netperf
       b. Receiver: netserver


----------
zhangleiqiang (Trump)

Best Regards
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