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Subject: Re: [Qemu-devel] is there a limit on the number of in-flight I/O
	operations?
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To: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org

On 07/18/2014 11:49 PM, Paolo Bonzini wrote:
> Il 19/07/2014 00:48, Chris Friesen ha scritto:
>>>>
>>>
>>> I forgot about "-drive ...,iops_max=NNN". :)
>>
>> I'm not sure it's actually useful though, since it specifies the max IO
>> operations per second, not the maximum number of in-flight operations.
>
> No, that's "-drive iops=NNN".  QEMU implements a leaky bucket algorithm,
> where "iops_max" gives the size of the bucket and "iops" gives the
> refill rate.

Does it track in-flight operations though?  Or just how many operations 
can be requested in a given amount of time?

If it tracks how many operations can be requested, then if the "iops" 
parameter is larger than what the server can maintain then the number of 
in-flight operations could still grow indefinitely.

I suppose I'll have to check the code. :)

Chris