[K12OSN] Re: 1.4 mbps on 100BaseT!

[Dean Weiten]

Hi there,

We had a similar (although not as bad) problem.  I had an LTSP expert come
down and have a look.  The first thing he did was log in as root and do
"netstat -i" and look at the fifth and ninth columns, those headed with
"RX-ERR" and "TX-ERR".  We were losing Ethernet packets due to errors.

It turned out that the server's motherboard didn't like the interrupt load
with APIC enabled.  "APIC" is the advanced priority interrupt controller, a
fancy technology to allow an interrupt-based system to support more
interrupts than the original AT (which had something like only 14 interrupt
lines but some were already spoken for so you had even less).

The answer?  Add "noapic" to the end of the "kernel" line in
/boot/grub/grub.conf, then reboot.  We took the additional step of disabling
the APIC support in the BIOS as well.  I actually made a new copy of the
boot entry in grub.conf, just in case.

Here are our grub.conf file contents.  "SCCS" is the abbreviation we use for
our school - it's just a minor customization that I've done to change the
names of the boot sections in the file.

    #boot=/dev/hda
    default=0
    timeout=10
    splashimage=(hd0,0)/grub/splash.xpm.gz
    title SCCS Application Server (2.4.22-1.2199.nptlsmp)
     root (hd0,0)
     kernel /vmlinuz-2.4.22-1.2199.nptlsmp ro root=LABEL=/ rhgb noapic
     initrd /initrd-2.4.22-1.2199.nptlsmp.img
    title SCCS Application Server APIC (2.4.22-1.2199.nptlsmp)
     root (hd0,0)
     kernel /vmlinuz-2.4.22-1.2199.nptlsmp ro root=LABEL=/ rhgb
     initrd /initrd-2.4.22-1.2199.nptlsmp.img
    title SCCS Application Server Single APIC (2.4.22-1.2199.nptl)
     root (hd0,0)
     kernel /vmlinuz-2.4.22-1.2199.nptl ro root=LABEL=/ rhgb
     initrd /initrd-2.4.22-1.2199.nptl.img
    title SCCS Application Server OLD (2.4.22-1.2166.nptlsmp)
     root (hd0,0)
     kernel /vmlinuz-2.4.22-1.2166.nptlsmp ro root=LABEL=/ rhgb
     initrd /initrd-2.4.22-1.2166.nptlsmp.img
    title SCCS Application Server OLD Single (2.4.22-1.2166.nptl)
     root (hd0,0)
     kernel /vmlinuz-2.4.22-1.2166.nptl ro root=LABEL=/ rhgb
     initrd /initrd-2.4.22-1.2166.nptl.img

Of course, no warranties are expressed or implied.

Regards,

Dean Weiten
E-mail:   dmw at weiten.com