On Wed, Apr 19, 2017 at 8:03 AM, Michal Skrivanek <[email protected]> wrote:
> > Why not reserving regular hugepages for VMs on boot? Do you mean at hypervisor level? In this case it is what I'm doing normally for physical servers where I install Oracle RDBMS > then you can use > it with vdsm hook for that Oracle VM. Which hook are you referring? This one: http://www.ovirt.org/develop/developer-guide/vdsm/hook/hugepages/ ? In case is it still current? In the sense that I need to mount the hugetblfs virtual file system at hst level? The hook description seems low detailed... Normally if I want oracle user able to use huge pages on physical server, I have to specify # # Huge pages # vm.hugetlb_shm_group = 2000 # 18GB allocatable vm.nr_hugepages = 9216 # where 2000 is the group id for dba group, the main group of oracle user How to map this with vrtualization? Eg: 1) vm.hugetlb_shm_group at hypervisor side should be set to the group of the qemu user as the qemu-kvm process runs with it? 2) Then I have to set VM for VM the hugepages=xxx value in the hook and that will bypass the sysctl.conf configuration in the guest? 3) I presume I have to set the vm.hugetlb_shm_group parameter at guest level.... Thanks, Gianluca > It improves VM performance in > general, the only drawback is less flexibility since that memory can't > be used by others unless they specifically ask for hugepages. > This seems to confirm that I have to set a statich sysctl.conf entry at hypervisor level such as vm.nr_hugepages = YYYY > Also, I suppose you disable KSM, and I'm not sure about ballooning, > unless you need it I'd disable it too. > I kept the defaults at the moment that I suppose should be a) KSM disabled ksm has been configured to start by default as normally, but ksmtuned has been disabled: [g.cecchi@ov300 ~]$ sudo systemctl status ksm ● ksm.service - Kernel Samepage Merging Loaded: loaded (/usr/lib/systemd/system/ksm.service; enabled; vendor preset: enabled) Active: active (exited) since Tue 2017-04-11 11:07:28 CEST; 1 weeks 1 days ago Process: 976 ExecStart=/usr/libexec/ksmctl start (code=exited, status=0/SUCCESS) Main PID: 976 (code=exited, status=0/SUCCESS) CGroup: /system.slice/ksm.service Apr 11 11:07:28 ov300.datacenter.polimi.it systemd[1]: Starting Kernel Samepage Merging... Apr 11 11:07:28 ov300.datacenter.polimi.it systemd[1]: Started Kernel Samepage Merging. [g.cecchi@ov300 ~]$ sudo systemctl status ksmtuned ● ksmtuned.service - Kernel Samepage Merging (KSM) Tuning Daemon Loaded: loaded (/usr/lib/systemd/system/ksmtuned.service; disabled; vendor preset: disabled) Active: inactive (dead) [g.cecchi@ov300 ~]$ b) ballooning enabled for a newly created VM unless I explicitly disable it (at least I see this happens in 4.1.1) What to do for a) and b) to not interfere with huge pages? > The hook is being improved right now in master, but it should be > usable in stable too. > > I will be happy to test and verify and contribute to its description, as soon as I understand its usage.... Gianluca
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