[syslinux] Syslinux 4.04 gpxelinux.0 http performance problem with VMware VMs

[Pasi Kärkkäinen]

On Tue, May 08, 2012 at 08:44:01PM +0300, Pasi Kärkkäinen wrote:
> > > 
> > > Hello Pasi,
> > > 
> > > As I understand it, simply chain pxelinux.0 (from the 4.10-pre* line)
> > > to your PXE client as the boot file, and it'll speak HTTP if it's
> > > given an HTTP URI from the pxelinux.cfg/default (or client specific
> > > named) config file.
> > > 
> > 
> > Thanks for confirming that!
> > 
> > > I'd suspect that if you want to pull HTTP for the config file as well,
> > > you'd have to set your DHCP options accordingly, notably the pxelinux
> > > Path Prefix, or DHCP option 210, along with the "pxelinux magic"
> > > options.  Detailed here:
> > > http://www.syslinux.org/wiki/index.php/PXELINUX#Can_I_send_information_to_PXELINUX_via_special_options_in_the_DHCP_response.3F
> > > 
> > 
> > Yeah I've been pulling also the config file over HTTP with gpxelinux.0,
> > so I assume I need pretty much the same DHCP config/options when using 
> > the new pxelinux.0 from 4.10-pre*. 
> > 
> > > Been meaning to try it out myself since I downloaded the binaries a
> > > few days ago :)
> > > 
> > 
> > Good luck :) I'll try it today/tomorrow aswell.
> > 
> 
> I just tried with pxelinux.0 from syslinux-4.10-pre20.
> 
> Now I can get up to 6 MB/sec http download speed when using 
> vmxnet3 NIC in the PXE boot VM. 
> 
> If I use e1000 NIC in the PXE boot VM the speed is slower, 
> around 1.0 - 1.5 MB/sec.
> 
> So now it's better but still not quite there..
> 
> I can still see a lot of TCP retransmits on the http server (CentOS 6.2) side.
> While downloading 260 MB image over http I can see around 5900 TCP retransmits 
> happening on the http server! That doesn't sound right.. 
> 
> Can someone think of Linux network settings that might affect this on the http server side? 
> 

Actually it's all these counters from "netstat -s" that increase at (about) the same rate:

6583 segments retransmited
6243 times recovered from packet loss due to fast retransmit
6326 fast retransmits

Does that ring any bells to anyone? 
There are no errors or drops on the eth0 nic level (in ifconfig output).

Thanks,

-- Pasi