[Xen-users] X86_64 and 4GB RAM

["John Hannfield" <hal9020@xxxxxxxxx>]

Hello,
I have an odd problem on a dual processor, dual core Opteron system.
Obviosously it is x86_64 so should have no problem large amounts of
RAM. The system has 4 GB installed (2GB on each processor).

If I boot the system with a fresh install of Debian Etch it sees all the memory
fine. dmesg reports:

Memory: 4107008k/5242880k available (1929k kernel code, 86836k
reserved, 864k data, 176k init)

However if I boot a xen-3.0.3  kernel, it only sees about half of this:
The xen dmesg reports:

Memory: 183852k/270336k available (3531k kernel code, 77948k reserved,
1250k data, 208k init)

However  'xm info'  shows:

total_memory           : 3071


This is running a source install of Xen 3.0.3  with kernel 2.6.16.29
I have checked the kernel configuration that Etch uses, compared to my
Xen kernel,
and see that Etch is using "Discontiguos Memory" model, where as the only option
in the xen compile is "Flat Memory" model.  Also Etch is using NUMA,
which doesn't
seem to be an option during the xen kernel compile.

Surely, xen can access the full memory of this system?
Can anyone recommend any things to try?

My kernel config for "processor type and features" is below.
Etch kernel uses:

CONFIG_ARCH_DISCONTIGMEM_ENABLE=y
CONFIG_ARCH_DISCONTIGMEM_DEFAULT=y
CONFIG_ARCH_SPARSEMEM_ENABLE=y
CONFIG_SELECT_MEMORY_MODEL=y
# CONFIG_FLATMEM_MANUAL is not set
CONFIG_DISCONTIGMEM_MANUAL=y
# CONFIG_SPARSEMEM_MANUAL is not set
CONFIG_DISCONTIGMEM=y
CONFIG_FLAT_NODE_MEM_MAP=y

Whereas my Xen kernel config uses:

#
# Processor type and features
#
CONFIG_X86_PC=y
# CONFIG_X86_VSMP is not set
CONFIG_MK8=y
# CONFIG_MPSC is not set
# CONFIG_GENERIC_CPU is not set
CONFIG_X86_64_XEN=y
CONFIG_X86_NO_TSS=y
CONFIG_X86_NO_IDT=y
CONFIG_X86_L1_CACHE_BYTES=64
CONFIG_X86_L1_CACHE_SHIFT=6
CONFIG_X86_GOOD_APIC=y
# CONFIG_MICROCODE is not set
# CONFIG_X86_MSR is not set
# CONFIG_X86_CPUID is not set
CONFIG_X86_IO_APIC=y
CONFIG_X86_XEN_GENAPIC=y
CONFIG_X86_LOCAL_APIC=y
CONFIG_MTRR=y
CONFIG_SMP=y
CONFIG_PREEMPT_NONE=y
# CONFIG_PREEMPT_VOLUNTARY is not set
# CONFIG_PREEMPT is not set
# CONFIG_PREEMPT_BKL is not set
CONFIG_ARCH_FLATMEM_ENABLE=y
CONFIG_SELECT_MEMORY_MODEL=y
CONFIG_FLATMEM_MANUAL=y
# CONFIG_DISCONTIGMEM_MANUAL is not set
# CONFIG_SPARSEMEM_MANUAL is not set
CONFIG_FLATMEM=y
CONFIG_FLAT_NODE_MEM_MAP=y
# CONFIG_SPARSEMEM_STATIC is not set
CONFIG_SPLIT_PTLOCK_CPUS=4096
CONFIG_NR_CPUS=32
# CONFIG_HOTPLUG_CPU is not set
CONFIG_ARCH_ENABLE_MEMORY_HOTPLUG=y
CONFIG_SWIOTLB=y
# CONFIG_CRASH_DUMP is not set
CONFIG_PHYSICAL_START=0x100000
# CONFIG_SECCOMP is not set
# CONFIG_HZ_100 is not set
CONFIG_HZ_250=y
# CONFIG_HZ_1000 is not set
CONFIG_HZ=250
CONFIG_GENERIC_HARDIRQS=y
CONFIG_GENERIC_IRQ_PROBE=y
CONFIG_ISA_DMA_API=y
CONFIG_GENERIC_PENDING_IRQ=y

--

John

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