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Running 32 bit Rhel 6.5 with kernel 2.6.32-431.el6.i686 on a server with 46 Gb RAM and NUMA support.

CONFIG_X86_PAE=y

Intel(R) Xeon(R) CPU E5-2660 0 @ 2.20GHz

OS is not able to see more than 14GB RAM and lscpu not showing any NUMA nodes in output. numastat complains system as not NUMA aware.

config-2.6.32-431.el6.i686|grep -i numa

CONFIG_X86_NUMAQ is not set
CONFIG_NUMA is not set

free -lm

              total       used     free       shared    buffers     cached
Mem:         14682        697      13985          0         89        408
Low:           242        230         12
High:        14439        466      13972

numastat

sysfs not mounted or system not NUMA aware: No such file or directory

mount|grep sysfs

sysfs on /sys type sysfs (rw)
  • Can there be any limitation for 32 bit OS on NUMA systems?
  • Why is OS not able to access 46 GB(2^36 > 46 Gb) even with PAE,is it because of NUMA disabled?

On 64 bit its working fine.

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Can there be any limitation for 32 bit OS on NUMA systems?

cat /boot/config-2.6.32-431.el6.i686|grep -i numa

CONFIG_X86_NUMAQ is not set

CONFIG_NUMA is not set

Kernel is not compiled with NUMA Enabled.

Why is OS not able to access 46 GB(2^36 > 46 Gb) even with PAE,is it because of NUMA disabled?

RHEL 6 32 bit doesn't come with Huge mem support

http://www.redhat.com/resourcelibrary/articles/articles-red-hat-enterprise-linux-6-technology-capabilities-and-limits#note4

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