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6 Replies Latest reply: Oct 23, 2012 8:00 AM by user12273962 RSS

Hugepages in Oracle VM 3.0.3 environment

Kirill.Boyko Newbie
Currently Being Moderated
Hello!

Are there any official information on MOS about hugepages in PV Linux on OVM?
How can we turn on this feature for PV Guest VM? We are running one big database and it has some problems with pagetables. SR is opened on that.

VM Server Linux ovsru0240vh021 2.6.32.21-45.6xen
VM Server grub.conf
#boot=/dev/sda
default=0
timeout=5
title Oracle VM server (2.6.32.21-45.6xen)
root (hd0,0)
kernel /xen.gz dom0_mem=11110M allowhugepage
module /vmlinuz-2.6.32.21-45.6xen ro root=UUID=cd09ac72-3ccc-4dba-b7f7-9d7caa44904d
module /initrd-2.6.32.21-45.6xen.img


PV Guest VM Linux lnxru0240vg151 2.6.39-200.34.1.el6uek.x86_64
vm.cfg: superpages = 1
sysctl.conf: vm.nr_hugepages = 100
[root@lnxru0240vg151 ~]# cat /proc/meminfo | grep Huge
AnonHugePages: 0 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB


Thx for help in advance!

Regards, Kirill
  • 1. Re: Hugepages in Oracle VM 3.0.3 environment
    user459387 Newbie
    Currently Being Moderated
    Hello,

    I'm also interested in using hugepages for oracle database in Oracle VM environment.

    Little bit experimentation(xen source code) and googling give me xen boot parameter allowsuperpage=1

    Then with superpages = 1 in vm.cfg it was able to allocate HugePages in PV domU.
    domU OEL 6 with 2.6.39-200.29.2.el5uek
    AnonHugePages: 0 kB
    HugePages_Total: 100
    HugePages_Free: 100
    HugePages_Rsvd: 0
    HugePages_Surp: 0
    Hugepagesize: 2048 kB

    I didn't find any documentation, howto or examples using this in Oracle VM ( or generally with Xen).
    Any informations about benchmarks, stability and status of support of hugepages(superpages) in Oracle VM are welcome.

    All this was done on Oracle VM 3.1

    Karel
  • 2. Re: Hugepages in Oracle VM 3.0.3 environment
    user12273962 Pro
    Currently Being Moderated
    I don't "think" there is support on 3.1.1. There was support in 2.

    Either way....

    Arn't you using 64 bit? and why would you choose huge pages over AMM? You really should consider AMM before you even attempt to run Huge Pages on a 64 bit platform.
  • 3. Re: Hugepages in Oracle VM 3.0.3 environment
    Kirill.Boyko Newbie
    Currently Being Moderated
    Thank you Karel for valuable info
    I will try in my environment and post some feedback here

    Regards,
    Kirill
  • 4. Re: Hugepages in Oracle VM 3.0.3 environment
    user459387 Newbie
    Currently Being Moderated
    Hello,

    I've got some informations about AMM and Hugepages(with ASSM).

    We are preparing server (Oracle Vm hypervisor), that will host two large VMs (64bit OEL, 60+GB each). Each VM with cca 6 databases ( 2 with large SGA, rest smaller).
    Ability to use huge pages give us the posibility to reduce pagetable walks and pagetablesize, so CPU and RAM savings.

    I don't know what can give us the use of AMM in such a configuration?
    AMM can partition the RAM between database instances.

    Karel
  • 5. Re: Hugepages in Oracle VM 3.0.3 environment
    Kirill.Boyko Newbie
    Currently Being Moderated
    Hi Karel!

    I would definitely not recommend to use AMM in such configuration.
    Please use MOS to read about Hugepages and AMM support. AMM is not supported with Hugepages. Only ASMM is supported.

    You can read some valuable info about Linux, DB and memory management here:
    http://www.pythian.com/news/741/pythian-goodies-free-memory-swap-oracle-and-everything/
    http://kevinclosson.wordpress.com/2010/09/28/configuring-linux-hugepages-for-oracle-database-is-just-too-difficult-part-i/

    have fun :)

    Regards,
    Kirill
  • 6. Re: Hugepages in Oracle VM 3.0.3 environment
    user12273962 Pro
    Currently Being Moderated
    You may want to read article 361323.1 before you choose to do such. Pay attention to the "What if Not Enough HugePages Configured?" section.

    Either way... there is no talk of support for huge pages on 3.1.1. Have fun "tweaking your environment."