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Re: [RFC PATCH 0/8 v2] Summary on block IO throttle

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On 10/27/2011 11:45 PM, Eric Blake wrote:
On 10/27/2011 03:12 AM, Lei Li wrote:
1) Enable the blkio throttling in xml when guest is starting up.

Add blkio throttling in xml as follows:

<disk type='file' device='disk'>
<driver name='qemu' type='raw'/>
<source file='/var/lib/libvirt/images/kvm-one.img'/>
<target dev='vda' bus='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
<iotune bps='n'.../>
</disk>

2) Enable blkio throttling setting at guest running time.

virsh blkiothrottle<domain> <device> [--bps<number>] [--bps_rd<number>] \ [--bps_wr<number>] [--iops<number>] [--iops_rd<number>] [--iops_wr<number>]

3) The support to get the current block i/o throttling for a device - HMP/QMP.

virsh blkiothrottle<domain> <device>

Given that the XML is named <iotune> under <disk>, we should probably name the virsh command 'blkiotune' or 'disk-iotune', not 'blkiothrottle'.

Hi Eric, we used<iothrottle>  first, I changed it since Daniel P. Berrange
proposed<iotune>  for per-disk element instead of<iothrottle>  when we
discussed at RFC V1.

The command 'blkiotune' already exist, supported the cgroups
blkio-controller, which handles proportional shares and throughput/iops
limits on host block devices, global to the domain, but blkio throttling
is specified per-disk and can vary across multiple disks. They are different
two mechanism.

So how about use<iothrottle>  again? :)

Also, <iotune bps='n'.../> doesn't look right. This should be similar to the top-level XML. Here, taking into account the other proposal for per-block-device values (which can't be tied to individual <disk>):

<domain...>
<blkiotune>
<weight>800</weight>
<device>
<path>/path/to/device</path>
<weight>200</weight>
</device>
</blkiotune>
<devices>
<disk ...>
<iotune>
<bps>800</bps>
        ...
</iotune>
</disk>
</devices>
</domain>

OK. I will do it at v3.



  daemon/remote.c                 |   85 +++++++++++++++++
  include/libvirt/libvirt.h.in    |   25 +++++

Missing changes in docs/formatdomain.html.in (to describe the new XML), docs/schemas/domaincommon.rng (to validate the new xml), and tests/ (probably qemuxml2argvdata), to test it.



--
Lei

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