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

Pasi Kärkkäinen pasik at iki.fi
Tue May 8 07:27:49 PDT 2012


On Tue, May 08, 2012 at 09:26:12AM -0400, Andrew Bobulsky wrote:
> On Tue, May 8, 2012 at 8:24 AM, Pasi Kärkkäinen <pasik at iki.fi> wrote:
> > On Tue, May 08, 2012 at 02:05:31PM +0300, Pasi Kärkkäinen wrote:
> >> On Mon, May 07, 2012 at 09:53:35PM -0400, Gene Cumm wrote:
> >> > On Mon, May 7, 2012 at 4:40 PM, Pasi Kärkkäinen <pasik at iki.fi> wrote:
> >> > > Hello,
> >> > >
> >> > > In my testing environment I have two VMs on ESXi 5.0.
> >> > >
> >> > > VM A = dhcp/tftp/PXE/http server, running CentOS 6.2. Syslinux 4.04 with the included gpxelinux.0.
> >> > > VM B = PXE boot client.
> >> >
> >> > > Any ideas what's causing the bad performance and those continuous retransmits?
> >> > > Anything I should try to debug this?
> >> > >
> >> > > On baremetal with Intel NICs I've seen much better gpxelinux.0 download speeds over http.
> >> >
> >> > Syslinux 4.04 is obsolete and probably not worth debugging.  4.05 is
> >> > current and 4.10-pre20 is a beta with lwIP, a lightweight IP stack,
> >> > eliminating the need for gPXE if you only want HTTP downloads.  I've
> >> > already been testing 4.10-pre* in VMware VMs with success after my
> >> > patch.  I've seen a solid 45-70 MB/s after that patch on VMware VMs.
> >> >
> >>
> >> That sounds really nice! I'll have to try the new stuff.
> >>
> >
> > Oh, is there any documentation or examples about the new non-gPXE stuff?
> > Should I just use pxelinux.0 to get the LwIP http?
> >
> > I couldn't find anything with "grep -i lwip doc/*" in the git clone,
> > but maybe I'll start browsing the changelogs :)
> >
> >
> > Thanks,
> >
> > -- Pasi
> 
> 
> 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.

-- Pasi




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