[CentOS-virt] What kernel params to use with KVM hosts??

Steven Ellis steven.ellis at bulletin.net
Thu Mar 18 00:18:06 UTC 2010


carlopmart wrote:
> Steven Ellis wrote:
>   
>> carlopmart wrote:
>>     
>>> Hi all,
>>>
>>>   I order to reach maximum performance on my centos kvm hosts I have use these params:
>>>
>>>   - On /etc/grub.conf:
>>>
>>>     kernel /vmlinuz-2.6.18-164.11.1.el5 ro root=LABEL=/ elevator=deadline quiet
>>>
>>>   - On sysctl.conf
>>>
>>>    # Special network params
>>>    net.core.rmem_default = 8388608
>>>    net.core.wmem_default = 8388608
>>>    net.core.rmem_max = 16777216
>>>    net.core.wmem_max = 16777216
>>>    net.ipv4.tcp_rmem = 1048576 4194304 16777216
>>>    net.ipv4.tcp_wmem = 1048576 4194304 16777216
>>>
>>>
>>>    # Disable netfilter on bridges.
>>>    net.bridge.bridge-nf-call-ip6tables = 0
>>>    net.bridge.bridge-nf-call-iptables = 0
>>>    net.bridge.bridge-nf-call-arptables = 0
>>>
>>>    # Virtual machines special kernel params
>>>    vm.swappiness = 0
>>>   
>>>       
>> Care to explain some of your choices.
>>
>> In particular why
>>
>> vm.swappiness = 0
>>
>> and why elevator=deadline over noop.
>>
>> Steve
>>
>>     
>
> I use elevator=deadline on kvm host. Under kvm guests I use elevator=noop ...
>   
I agree with these settings

> vm.swappiness is heredated from vmware installations. Is it wrong??
>   
I don't know. I haven't done enough performance tests. Anyone else care
to comment?

Steve


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