topic Re: OEL 5.9 not recognizing total installed RAM. in Operating System - Linux

OEL 5.9 not recognizing total installed RAM.

Imran_K — Tue, 17 Dec 2013 06:52:52 GMT

Hi all,

we are facing problem after upgrading RAM to 64GB, previously our system was running with 32GB, with oracle enterprise linux 5.9.

recently we upgraded it to 64GB in the system hardware its showing all 64GB but from OS side its showing only 32GB.

How can i get all 64GB usable.

# uname -a

Linux XXXXXXXXXXXXX 2.6.18-348.el5xen #1 SMP Wed Jan 9 08:32:18 PST 2013 x86_64 x86_64 x86_64 GNU/Linux

]# cat /proc/meminfo

MemTotal: 33554432 kB

MemFree: 26679220 kB

Buffers: 203628 kB

Cached: 744152 kB

SwapCached: 0 kB

Active: 5372380 kB

Inactive: 535884 kB

HighTotal: 0 kB

HighFree: 0 kB

LowTotal: 33554432 kB

LowFree: 26679220 kB

SwapTotal: 33554424 kB

SwapFree: 33554424 kB

Dirty: 140 kB

Writeback: 0 kB

AnonPages: 4960656 kB

Mapped: 52028 kB

Slab: 150560 kB

PageTables: 31776 kB

NFS_Unstable: 0 kB

Bounce: 0 kB

CommitLimit: 50331640 kB

Committed_AS: 10139772 kB

VmallocTotal: 34359738367 kB

VmallocUsed: 18092 kB

VmallocChunk: 34359719735 kB

# dmidecode -t 16

# dmidecode 2.11

SMBIOS 2.7 present.

Handle 0x1000, DMI type 16, 23 bytes

Physical Memory Array

Location: System Board Or Motherboard

Use: System Memory

Error Correction Type: Single-bit ECC

Maximum Capacity: 384 GB

Error Information Handle: Not Provided

Number Of Devices: 12

Handle 0x1001, DMI type 16, 23 bytes

Physical Memory Array

Location: System Board Or Motherboard

Use: System Memory

Error Correction Type: Single-bit ECC

Maximum Capacity: 384 GB

Error Information Handle: Not Provided

Number Of Devices: 12

dmidecode -t 17 |grep Size

Size: 8192 MB

Size: No Module Installed

Size: 8192 MB

Size: No Module Installed

Size: 8192 MB

Size: No Module Installed

Size: 8192 MB

Size: No Module Installed

Size: 8192 MB

Size: No Module Installed

Size: 8192 MB

Size: No Module Installed

Size: 8192 MB

Thanks !

Re: OEL 5.9 not recognizing total installed RAM.

Matti_Kurkela — Tue, 17 Dec 2013 14:51:54 GMT

> # uname -a

> Linux XXXXXXXXXXXXX 2.6.18-348.el5xen #1 SMP[...]

You're running a Xen kernel, so the "missing" memory might be in use by other Xen domains (=VMs), or kept free by the Xen hypervisor so that you can add a new domain.

What is the output of "xm info | grep memory" command?

Are you using the "dom0_mem" boot option in /boot/grub/grub.conf?

This might be useful. It is written for Oracle VM, but is valid for other Xen setups too:

https://blogs.oracle.com/wim/entry/understanding_memory_allocation_in_oracle

Re: OEL 5.9 not recognizing total installed RAM.

Imran_K — Wed, 18 Dec 2013 05:08:32 GMT

thanks for your replay, we didn't configure any domains in this server and the output of the said command

What is the output of "xm info | grep memory" command?

xm info |grep memory
Error: Unable to connect to xend: No such file or directory. Is xend running?

Are you using the "dom0_mem" boot option in /boot/grub/grub.conf?

#boot=/dev/cciss/c0d0
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title Oracle Linux Server (2.6.18-348.el5xen)
        root (hd0,0)
        kernel /xen.gz-2.6.18-348.el5
        module /vmlinuz-2.6.18-348.el5xen ro root=/dev/VolGroup00/LogVol00 rhgb
quiet

Re: OEL 5.9 not recognizing total installed RAM.

Matti_Kurkela — Wed, 18 Dec 2013 07:41:14 GMT

With that /boot/grub/grub.conf, you are running Xen as the hypervisor and OEL 5.9 as its dom0 domain (= the special Xen domain that manages the physical I/O). The dom0 domain is created automatically, since it must always exist whenever a Xen environment is running.

The memory restriction is a limitation of the Xen hypervisor: the dom0 domain can have a maximum of 32 GiB of memory in this version. The rest is available for domU domain(s). Since the applications should normally be run in domU domains, not in dom0, this is not normally an issue.

(In a normal situation, you might even want to restrict your dom0 size to smaller than 32 GiB, to leave more memory for your domUs - that can provide better performance than relying on dom0 memory ballooning to auto-manage memory between domUs and dom0.)

If you are not planning to run any domU domains, why are you running the Xen kernel at all? In that situation, I think it only adds extra restrictions, complexity and overhead for you.

If you installed your system with the "everything" option, this is one of the reasons why that is not always a good idea.