[CentOS] Not seeing all memory in CentOS 5.1 x86_64

John R Pierce pierce at hogranch.com
Wed Jun 11 00:54:07 UTC 2008


Ruslan Sivak wrote:
> I'm running CentOS 5.1 with all updates, and the xen kernel.  For some 
> reason the OS is not seeing the full amount of ram.
> #uname -a
> Linux CentOS-VM-A 2.6.18-53.1.21.el5xen #1 SMP Tue May 20 10:03:27 EDT 
> 2008 x86_64 x86_64 x86_64 GNU/Linux
>
> # free
>             total       used       free     shared    buffers     cached
> Mem:       6104064    3445136    2658928          0    1412236    1515032
> -/+ buffers/cache:     517868    5586196
> Swap:      2031608          0    2031608

whats cat /proc/meminfo   say?

what do you see at the top of `dmesg` relating to memory (first 100 or 
so lines).


like, on a x86_64 RHEL4 quad opteron 850  box I have here w/ 8GB, I see...

# free
             total       used       free     shared    buffers     cached
Mem:       8005256    7953140      52116          0      78172    7287724
-/+ buffers/cache:     587244    7418012
Swap:      8385920        208    8385712

# dmesg|more
Bootdata ok (command line is ro root=LABEL=/ rhgb quiet)
Linux version 2.6.9-55.0.6.ELsmp 
(brewbuilder at ls20-bc2-14.build.redhat.com) (gcc version 3.4.6 20060404 
(Red Hat 3.4.6-8)) #1
 SMP Thu Aug 23 11:13:21 EDT 2007
BIOS-provided physical RAM map:
 BIOS-e820: 0000000000000000 - 000000000009f400 (usable)
 BIOS-e820: 000000000009f400 - 00000000000a0000 (reserved)
 BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
 BIOS-e820: 0000000000100000 - 00000000f57fa000 (usable)
 BIOS-e820: 00000000f57fa000 - 00000000f5800000 (ACPI data)
 BIOS-e820: 00000000fdc00000 - 00000000fdc01000 (reserved)
 BIOS-e820: 00000000fdc10000 - 00000000fdc11000 (reserved)
 BIOS-e820: 00000000fdc20000 - 00000000fdc21000 (reserved)
 BIOS-e820: 00000000fdc30000 - 00000000fdc31000 (reserved)
 BIOS-e820: 00000000fec00000 - 00000000fec01000 (reserved)
 BIOS-e820: 00000000fec10000 - 00000000fec11000 (reserved)
 BIOS-e820: 00000000fec20000 - 00000000fec21000 (reserved)
 BIOS-e820: 00000000fee00000 - 00000000fee10000 (reserved)
 BIOS-e820: 00000000ff800000 - 0000000100000000 (reserved)
 BIOS-e820: 0000000100000000 - 00000001fffff000 (usable)
ACPI: RSDP (v002 HP                                    ) @ 
0x00000000000f4f20
ACPI: XSDT (v001 HP     A01      0x00000002 Ò 0x0000162e) @ 
0x00000000f57fa400
ACPI: FADT (v003 HP     A01      0x00000002 Ò 0x0000162e) @ 
0x00000000f57fa480
ACPI: MADT (v001 HP     00000083 0x00000002  0x00000000) @ 
0x00000000f57fa100
ACPI: SPCR (v001 HP     SPCRRBSU 0x00000001 Ò 0x0000162e) @ 
0x00000000f57fa200
ACPI: SRAT (v001 HP     A01      0x00000001  0x00000000) @ 
0x00000000f57fa280
ACPI: DSDT (v001 HP         DSDT 0x00000001 MSFT 0x02000001) @ 
0x0000000000000000
Scanning NUMA topology in Northbridge 24
Number of nodes 4 (30030)
Node 0 MemBase 0000000000000000 Limit 000000007fffffff
Node 1 MemBase 0000000080000000 Limit 00000000ffffffff
Node 2 MemBase 0000000100000000 Limit 000000017fffffff
Node 3 MemBase 0000000180000000 Limit 00000001fffff000
Using 22 for the hash shift. Max addr is 1fffff000
Using node hash shift of 22
Bootmem setup node 0 0000000000000000-000000007fffffff
Bootmem setup node 1 0000000080000000-00000000ffffffff
Bootmem setup node 2 0000000100000000-000000017fffffff
Bootmem setup node 3 0000000180000000-00000001fffff000
On node 0 totalpages: 524287
  DMA zone: 4096 pages, LIFO batch:1
  Normal zone: 520191 pages, LIFO batch:16
  HighMem zone: 0 pages, LIFO batch:1
On node 1 totalpages: 524287
  DMA zone: 0 pages, LIFO batch:1
  Normal zone: 524287 pages, LIFO batch:16
  HighMem zone: 0 pages, LIFO batch:1
On node 2 totalpages: 524287
  DMA zone: 0 pages, LIFO batch:1
  Normal zone: 524287 pages, LIFO batch:16
  HighMem zone: 0 pages, LIFO batch:1
On node 3 totalpages: 524287
  DMA zone: 0 pages, LIFO batch:1
  Normal zone: 524287 pages, LIFO batch:16
  HighMem zone: 0 pages, LIFO batch:1
DMI 2.3 present.
ACPI: PM-Timer IO Port: 0x908
ACPI: Local APIC address 0xfee00000
ACPI: LAPIC (acpi_id[0x00] lapic_id[0x00] enabled)
Processor #0 15:5 APIC version 16
ACPI: LAPIC (acpi_id[0x01] lapic_id[0x01] enabled)
Processor #1 15:5 APIC version 16
ACPI: LAPIC (acpi_id[0x02] lapic_id[0x02] enabled)
Processor #2 15:5 APIC version 16
ACPI: LAPIC (acpi_id[0x03] lapic_id[0x03] enabled)
Processor #3 15:5 APIC version 16
ACPI: LAPIC (acpi_id[0x04] lapic_id[0x04] disabled)
ACPI: LAPIC (acpi_id[0x05] lapic_id[0x05] disabled)
ACPI: LAPIC (acpi_id[0x06] lapic_id[0x06] disabled)
ACPI: LAPIC (acpi_id[0x07] lapic_id[0x07] disabled)
ACPI: LAPIC_NMI (acpi_id[0xff] high edge lint[0x1])
Setting APIC routing to flat
ACPI: IOAPIC (id[0x04] address[0xfec00000] gsi_base[0])
IOAPIC[0]: apic_id 4, version 17, address 0xfec00000, GSI 0-23
ACPI: IOAPIC (id[0x05] address[0xfec10000] gsi_base[24])
IOAPIC[1]: apic_id 5, version 17, address 0xfec10000, GSI 24-27
ACPI: IOAPIC (id[0x06] address[0xfec20000] gsi_base[28])
IOAPIC[2]: apic_id 6, version 17, address 0xfec20000, GSI 28-31
ACPI: IOAPIC (id[0x07] address[0xfdc00000] gsi_base[32])
IOAPIC[3]: apic_id 7, version 17, address 0xfdc00000, GSI 32-35
ACPI: IOAPIC (id[0x08] address[0xfdc10000] gsi_base[36])
IOAPIC[4]: apic_id 8, version 17, address 0xfdc10000, GSI 36-39
ACPI: IOAPIC (id[0x09] address[0xfdc20000] gsi_base[40])
IOAPIC[5]: apic_id 9, version 17, address 0xfdc20000, GSI 40-43
ACPI: IOAPIC (id[0x0a] address[0xfdc30000] gsi_base[44])
IOAPIC[6]: apic_id 10, version 17, address 0xfdc30000, GSI 44-47
ACPI: INT_SRC_OVR (bus 0 bus_irq 0 global_irq 2 high edge)
ACPI: IRQ0 used by override.
ACPI: IRQ2 used by override.
ACPI: IRQ9 used by override.
Using ACPI (MADT) for SMP configuration information
Allocating PCI resources starting at f6000000 (gap: f5800000:8400000)
Checking aperture...
CPU 0: aperture @ f30e000000 size 32 MB
Aperture from northbridge cpu 0 too small (32 MB)
No AGP bridge found
Your BIOS doesn't leave a aperture memory hole
Please enable the IOMMU option in the BIOS setup
This costs you 64 MB of RAM
Mapping aperture over 65536 KB of RAM @ 4000000
Built 4 zonelists
Kernel command line: ro root=LABEL=/ rhgb quiet console=tty0
Initializing CPU#0
PID hash table entries: 4096 (order: 12, 131072 bytes)
time.c: Using 3.579545 MHz PM timer.
time.c: Detected 2396.906 MHz processor.
Console: colour VGA+ 80x25
Dentry cache hash table entries: 2097152 (order: 12, 16777216 bytes)
Inode-cache hash table entries: 1048576 (order: 11, 8388608 bytes)
Memory: 8003652k/8388604k available (2115k kernel code, 0k reserved, 
1306k data, 208k init)
.......




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