Large page (huge pages) series four---Transparent hugepages

Source: Internet
Author: User

Starting from Redhat 6, OEL 6, SLES One and UEK2 kernels, the system lacks the capital to enable Transparent Hugepages: Used to improve memory management
The Performance transparent large page (Transparent hugepages) is similar to the large page feature in previous versions, the main difference being: Transparent hugepages can be configured in real time,
No restart is required to make the configuration effective;
Transparent large pages (Transparent hugepages) mainly use khugepaged thread, whereas the previous large pages are pre-allocated by the time the system is started;

However, Oracle does not recommend that we use Redhat 6, OEL 6, SLES One and UEK2 kernels transparent large pages (Transparent hugepages),
Because there are some problems with transparent large pages (Transparent hugepages):
1. Transparent large pages (Transparent hugepages) in a RAC environment can cause abnormal node restarts, and performance issues;
2. In a stand-alone environment, transparent large pages (Transparent hugepages) can also cause some abnormal performance problems;




----Take Red Hat 6.0 as an example:
Method One:
Enabled by default: [Always]---indicates that transparent large pages are enabled
[Email protected] redhat_transparent_hugepage]# cat/sys/kernel/mm/redhat_transparent_hugepage/enabled
[Always] madvise never


Disabled state:
[Email protected] redhat_transparent_hugepage]# cat/sys/kernel/mm/redhat_transparent_hugepage/enabled
Always madvise [never]


Method Two:
[[email protected] redhat_transparent_hugepage]# grep anonhugepages/proc/meminfo
anonhugepages:143360 KB
If anonhugepages > 0 also indicates that transparent large pages are enabled;




----How to disable transparent large pages
Method One (priority selection):

Add a row of records in/etc/grub.conf:


Transparent_hugepage=never

And then restart




Method Two:
Configure/etc/rc.local and then restart the server:
If Test-f/sys/kernel/mm/redhat_transparent_hugepage/enabled; Then
echo Never >/sys/kernel/mm/redhat_transparent_hugepage/enabled
Fi
If Test-f/sys/kernel/mm/redhat_transparent_hugepage/defrag; Then
echo Never >/sys/kernel/mm/redhat_transparent_hugepage/defrag
Fi


Large page (huge pages) series four---Transparent hugepages

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