[Bridge] Linux Bridge is slow ?

[ratheesh kannoth]

I have two virtual machine  VM1  and VM2 , which are running on
ubuntu.  Both VM are running  ubunutu. I bridged vnet0 and vnet1  in a
linux bridge on host machine.
 brctl addbr virbr0
 brctl addif  virbr0 vnet0
 brctl addif  virbr0  vnet1

I did a wget of  1.9G file from VM1 to VM2. it took 1 minute 43 sec at
18.6mbps to transfer the file.

I used the attached program ( which is using epoll ) to read and write
packets.  This program will register two network interfaces ( tap77
and tap88 ) with linux stack and will read packets from corresponding
file descriptor in userspace and write it in other.  I bridged
tap77 and vnet0  together  and  tap88 and vnet1 together using a
openvswitch bridge. Her i added an overhead  read, write system call
and  copy_to_user, copy_from_user  copies  in  both directions. [ from
vm1 to vm2  & vm2 to vm1 ] compared to linux bridge implementation
mentioned first.

when i ran wget test. It took less time.  1.9G file from VM1 to VM2.
it took 1 minute 39 sec at 19.3 mbps to transfer the file.

Does that mean that linux bridge is introducing a lot of delay ? i
thought it should be really fast ...any clue or hint is really
appreciated ?


Thanks,
Ratheesh
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