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Re: [Qemu-discuss] [dpdk-dev] Will huge page have negative effect on gue

From: Pavel Shirshov
Subject: Re: [Qemu-discuss] [dpdk-dev] Will huge page have negative effect on guest vm in qemu enviroment?
Date: Tue, 20 Jun 2017 23:15:29 -0700

Hi Sam,

Below I'm saying about KVM. I don't have experience with vbox and others.
1. I'd suggest don't use dpdk inside of VM if you want to see best
perfomance on the box.
2. huge pages enabled globally will not have any bad effect to guest
OS. Except you have to enable huge pages inside of VM and provide real
huge page for VM's huge pages from the host system. Otherwise dpdk
will use "hugepages" inside of VM, but this "huge pages" will not real
ones. They will be constructed from normal pages outside. Also when
you enable huge pages OS will reserve them from start and your OS will
not able use them for other things. Also you can't swap out huge
pages, KSM will not work for them and so on.
3. You can enable huge pages just for one numa node. It's impossible
to enable them just for one core. Usually you reserve some memory for
hugepages when the system starts and you can't use this memory in
normal applications unless normal application knows how to use them.

Also why it didn't work inside of the docker?

On Tue, Jun 20, 2017 at 8:35 PM, Sam <address@hidden> wrote:
> BTW, we also think about use ovs-dpdk in docker enviroment, but test result
> said it's not good idea, we don't know why.
> 2017-06-21 11:32 GMT+08:00 Sam <address@hidden>:
>> Hi all,
>> We plan to use DPDK on HP host machine with several core and big memory.
>> We plan to use qemu-kvm enviroment. The host will carry 4 or more guest vm
>> and 1 ovs.
>> Ovs-dpdk is much faster then normal ovs, but to use ovs-dpdk, we have to
>> enable huge page globally.
>> My question is, will huge page enabled globally have negative effect on
>> guest vm's memory orperate or something? If it is, how to prevent this, or
>> could I enable huge page on some core or enable huge page for a part of
>> memory?
>> Thank you~

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