[ovirt-users] Question about Huge Pages

Gianluca Cecchi gianluca.cecchi at gmail.com
Tue Apr 18 16:03:14 UTC 2017


Hello,
I'm testing virtualization of some Oracle servers.
I have 4.1.1 with CentOS 7.3 servers as hypervisors.
Typically on physical Oracle servers I configure huge pages for Oracle
memory areas.
In particular I disable Transparent Huge Pages, because they are known to
be in conflict with Oracle performances, both in RAC and in standalone
configurations.
In RHEL systems I configure "transparent_hugepage=never" boot parameter,
while in Oracle Linux OS uek kernels it is already disabled by default.
I notice that in CentOS 7.3, by default, transparent huge pages are
configured:

[root at ov300 ~]# cat /proc/meminfo | grep -i huge
AnonHugePages:  17006592 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
[root at ov300 ~]#

I'm going to configure a VM with 64Gb of ram and with an Oracle RDBMS that
would have 16Gb of SGA.
I suspect that I could have problems if I dont' change configuration at
hypervisor level...

What do you think about this subject?
Is there any drawback if I manually configure the hypervisors to boot with
 the "transparent_hugepage=never" boot parameter?

Thanks in advance,
Gianluca
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