Is the Transparent Huge Pages (THP) feature enabled on RHEL 6 (x86) 32-bit architecture, also enabled on RHEL 5?

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Linux 6 (x86) 32-bit
  • Red Hat Enterprise Linux 5 (x86/x86_64) 32/64-bit
  • Transparent Huge Pages (THP)
  • redhat_transparent_hugepage

Issue

  • Is Transparent Huge Pages (THP) feature enabled on Red Hat Enterprise Linux 6 (x86) 32-bit architecture ?
  • Why Red Hat Enterprise Linux 6 (x86) 32-bit server does not have "redhat_transparent_hugepage" directory inside /sys/kernel/mm/?
    Eg:
# cat /sys/kernel/mm/redhat_transparent_hugepage/{defrag,enabled}
cat: /sys/kernel/mm/redhat_transparent_hugepage/defrag: No such file or directory
cat: /sys/kernel/mm/redhat_transparent_hugepage/enabled: No such file or directory
  • Is Transparent Huge Pages (THP) feature enabled on Red Hat Enterprise Linux 5 (x86/x86_64) 32/64-bit architecture ?

Resolution

  • The Transparent Huge Pages (THP) feature is not present on the 32-bit (x86) version of Red Hat Enterprise Linux 6. Install the 64-bit (x86_64) version to enable this feature.
  • The Transparent Huge Pages (THP) feature is not present on the 32/64-bit (x86/x86_64) version of Red Hat Enterprise Linux 5.

Root Cause

  • The kernel configuration item "CONFIG_TRANSPARENT_HUGEPAGE" is not present in Red Hat Enterprise Linux 6 (x86).

    # grep -i huge /boot/config-2.6.32-358.el6.i686 
CONFIG_HUGETLBFS=y
CONFIG_HUGETLB_PAGE=y

  • The kernel configuration item "CONFIG_TRANSPARENT_HUGEPAGE" is enabled on Red Hat Enterprise Linux 6 (x86_64).

    # grep -i huge /boot/config-2.6.32-279.9.1.el6.x86_64 
CONFIG_TRANSPARENT_HUGEPAGE=y
CONFIG_HUGETLBFS=y
CONFIG_HUGETLB_PAGE=y

# grep -i huge /boot/config-2.6.18-194.el5
CONFIG_HUGETLBFS=y
CONFIG_HUGETLB_PAGE=y

# uname -a
Linux localhost 2.6.18-194.el5 #1 SMP Tue Mar 16 21:52:39 EDT 2010 x86_64 x86_64 x86_64 GNU/Linux

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