目前与云主机限速相关的内容共有三处：
neutron qos-xxx命令
neutron qos-xxx命令，通过neutron qos的形式为云主机port绑定相应的网络限速策略（对应弹性公网IP）
通过flavor对云主机进行默认限速：
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命令如下：
nova flavor-key m1.small set quota:vif_inbound_average=10240
nova flavor-key m1.small set quota:vif_outbound_average=10240
这儿的网络QoS是直接使用libvirt提供的参数来实现的：（http://www.libvirt.org/formatnetwork.html） 最终落在libvirt里面实现的配置如下
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<forward mode='nat' dev='eth0'/>
<bandwidth>
<inbound average='1000' peak='5000' burst='5120'/>
<outbound average='128' peak='256' burst='256'/>
</bandwidth>
云硬盘限速（动态）
由于不同规格云硬盘的限速要求差异，云硬盘采用公式进行限速； 对cinder进行二次开发后，在cinder.conf中配置相应的限速参数，根据创建的云硬盘大小不同，计算出不同的限速值，最后落到libvirt中生效如下：
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<disk type='network' device='disk'>
<driver name='qemu' type='raw' cache='none' discard='unmap'/>
<source protocol='rbd' name='ebs_ceph_ssd_sys/volume-6347f0d3-b2b1-41b2-a2b4-e75c19a9cba9'>
<host name='10.203.135.1' port='6789'/>
<host name='10.203.135.8' port='6789'/>
<host name='10.203.135.15' port='6789'/>
</source>
<target dev='sda' bus='scsi'/>
<iotune>
<total_bytes_sec>146800640</total_bytes_sec>
<total_iops_sec>2800</total_iops_sec>
</iotune>
<serial>6347f0d3-b2b1-41b2-a2b4-e75c19a9cba9</serial>
<wwn>004439433801266d</wwn>
<alias name='scsi0-0-0-0'/>
<address type='drive' controller='0' bus='0' target='0' unit='0'/>
</disk>
参考官方文档，flavor中支持以下tuning参数：
**Optional metadata keys: **
| CPU limits | quota:cpu_shares |
|---|---|
| quota:cpu_period | |
| quota:cpu_limit | |
| quota:cpu_reservation | |
| quota:cpu_quota | |
| Disk tuning | quota:disk_read_bytes_sec |
| quota:disk_read_iops_sec | |
| quota:disk_write_bytes_sec | |
| quota:disk_write_iops_sec | |
| quota:disk_total_bytes_sec | |
| quota:disk_total_iops_sec | |
| Bandwidth I/O | quota:vif_inbound_average |
| quota:vif_inbound_burst | |
| quota:vif_inbound_peak | |
| quota:vif_outbound_average | |
| quota:vif_outbound_burst | |
| quota:vif_outbound_peak | |
| Watchdog behavior | hw:watchdog_action |
| Random-number | generator hw_rng:allowed |
| hw_rng:rate_bytes | |
| hw_rng:rate_period |
