[syslinux] PXE boot from KVM VM is very slow

[H. Peter Anvin]

On 04/30/2010 09:23 AM, Galia Lisovskaya wrote:
> Hi all, i have trouble to PXE boot KVM-based (network of Linux-bridge)
> Virtual Machines: very slow transfer pxelinux.cfg.
> 
> ====== tcpdump on KVM host system ====
> [root at kvm-test01 ~]# tcpdump -i virbr1 | grep -v ssh | grep 10.0.5.187
> tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
> listening on virbr1, link-type EN10MB (Ethernet), capture size 96 bytes
> 
> 17:57:29.809278 IP 10.0.5.50 > 10.0.5.187: ICMP echo request, id 189,
> seq 0, length 28
> 17:57:30.181841 IP 10.0.5.50.bootps > 10.0.5.187.bootpc: BOOTP/DHCP,
> Reply, length: 300
> 17:57:32.744740 IP 10.0.5.187.bootpc > 255.255.255.255.bootps:
> BOOTP/DHCP, Request from 00:95:12:7e:ee:71 (oui Unknown), length: 548
> 17:57:32.755528 IP 10.0.5.50.bootps > 10.0.5.187.bootpc: BOOTP/DHCP,
> Reply, length: 300
> 17:57:32.782129 arp who-has 10.0.5.25 tell 10.0.5.187
> 17:57:32.782619 IP 10.0.5.187.wizard > 10.0.5.25.tftp:  33 RRQ
> "/pxelinux.0" octet blksize 1432
> 17:57:32.784308 IP 10.0.5.25.55214 > 10.0.5.187.wizard: UDP, length 15
> 17:57:32.784356 IP 10.0.5.187.wizard > 10.0.5.25.55214: UDP, length 4
> 17:57:32.784757 IP 10.0.5.25.55214 > 10.0.5.187.wizard: UDP, length 1436
> 17:57:33.784859 IP 10.0.5.25.55214 > 10.0.5.187.wizard: UDP, length 1436
> 17:57:35.784808 IP 10.0.5.25.55214 > 10.0.5.187.wizard: UDP, length 1436
> 17:57:37.783500 arp who-has 10.0.5.187 tell 10.0.5.50
> 17:57:37.790747 arp reply 10.0.5.187 is-at 00:95:12:7e:ee:71 (oui Unknown)
> 17:57:39.784733 IP 10.0.5.25.55214 > 10.0.5.187.wizard: UDP, length 1436
> 17:57:42.903369 IP 10.0.5.187.globe > 10.0.5.25.55214: UDP, length 4
> 17:57:42.903518 IP 10.0.5.25 > 10.0.5.187: ICMP 10.0.5.25 udp port
> 55214 unreachable, length 40
> 17:57:47.783601 IP 10.0.5.25.55214 > 10.0.5.187.wizard: UDP, length 1436
> 17:58:03.410473 IP 10.0.5.187.2003 > 10.0.5.25.55214: UDP, length 4
> 17:58:03.410628 IP 10.0.5.25 > 10.0.5.187: ICMP 10.0.5.25 udp port
> 55214 unreachable, length 40
> 17:58:03.781252 IP 10.0.5.25.55214 > 10.0.5.187.wizard: UDP, length 1436
> 17:58:08.409875 arp who-has 10.0.5.187 tell 10.0.5.50
> 17:58:08.409933 arp reply 10.0.5.187 is-at 00:95:12:7e:ee:71 (oui Unknown)
> 

You're having performance problems long before pxelinux.0 is even loaded.

	-hpa