6 Replies Latest reply: Oct 23, 2012 10:00 AM by user12273962 RSS

    Hugepages in Oracle VM 3.0.3 environment

    Kirill.Boyko
      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
          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
            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
              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
                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
                  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
                    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."