RE: [Xen-users] FIXED!!! amd64 system only seeing 3.5gb instead of 4gb of memory

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: James Harper [mailto:james.harper@xxxxxxxxxxxxxxxx] 
> Sent: 17 June 2007 13:01
> To: Petersson, Mats; xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: RE: [Xen-users] FIXED!!! amd64 system only seeing 
> 3.5gb instead of 4gb of memory
> 
> > >
> > > (XEN) Command line: /xen-3.1.0-1-amd64.gz
> > > (XEN)  0000000000000000 - 000000000009f000 (usable)
> > > (XEN)  0000000000100000 - 00000000dfff0000 (usable)
> > > (XEN) System RAM: 3583MB (3669564kB)
> > > (XEN) Xen heap: 13MB (14176kB)
> > > (XEN) Domain heap initialised: DMA width 32 bits
> > 
> > So that tells us that Xen is doing exactly what the BIOS/Grub says -
> and
> > of course, GRUB does things differently for Xen and a normal Linux
> > distro, simply because it's using a different model of booting.
> 
> I applied the patch mentioned here
> "http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=419994"; and 
> rebooted,
> and now xm dmesg says:
> 
> "
> (XEN) Command line: /xen-3.1.0-1-amd64.gz
> (XEN)  0000000000000000 - 000000000009f000 (usable)
> (XEN)  000000000009fc00 - 00000000000a0000 (reserved)
> (XEN)  00000000000e0000 - 0000000000100000 (reserved)
> (XEN)  0000000000100000 - 00000000dfff0000 (usable)
> (XEN)  00000000dfff0000 - 00000000dfffe000 (ACPI data)
> (XEN)  00000000dfffe000 - 00000000e0000000 (ACPI NVS)
> (XEN)  00000000fec00000 - 00000000fec01000 (reserved)
> (XEN)  00000000fee00000 - 00000000fef00000 (reserved)
> (XEN)  00000000ff780000 - 0000000100000000 (reserved)
> (XEN)  0000000100000000 - 0000000120000000 (usable)
> (XEN) System RAM: 4095MB (4193852kB)
> "
> 
> Which is a much healthier looking memory map, and I'm now seeing the
> right amount of memory!
> 
> The fix makes me think that the bug is a bit heisenbug-ish... but it
> works for me.

Yes, it looks like a "compiler issue" that is fixed by forcing the
compiler to not optimize the variable by using volatile - not the ideal
solution, but I guess fixing the compiler may be even more difficult.
[Not knowing what the code looks like - but I suppose the "cont"
variable isn't updated by an interrupt or external hardware!]

--
Mats
> 
> James
> 
> 
> 
> 



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