[ipxe-devel] Use iPXE's UNDI interface to read file from server very slow on virtualized guest unit

Wang, Junhua H. (NSN - CN/Hangzhou) junhua.h.wang at nsn.com
Tue Feb 25 01:52:44 UTC 2014

HI, All:
   We have a virtual machine which run on KVM, qemu on linux by SR-IOV. It(guest unit) use PXE to load bootloader by tftp, and then the bootloader will use UNDI interface to load other files from the server and then startup the OS.
   Our problem is that when we use UNDI interface(from PXE) to load files, it's very slow.
   For example, after the guest os start to ready state(linux), we use scp cmd to copy the image from the server, it's very quick. But in the PXE phase, we use similiar method to copy the image from
   the server, it's very slow. Everytime, the UNDI need much more time to get the packet than in linux phase. From the data we captured by wireshark on the Ethernet port of the host machine,
   we found the data already come to the ethernet port, but the guest unit can't get the packet after a long time delay.
   We use SR-IOV mechinsm to do virtualization.
   The Ethernet driver we use in the PXE is igbvf.
   Our colusion is that:
                1) the Host machine should be no problem since the speed is very quick after the guest unit startup to ready(linux).
                2) Our bootloader should be no problem, our bootloader try many times to read the packet from the port, but can't until long time delay.
                Do you experts have some suggestions about where the problem may be? thanks very much! I need your help!
Br, Jonny

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