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Date: Sat, 19 Jul 2014 10:45:37 +0200
From: =?iso-8859-1?Q?Beno=EEt?= Canet <benoit.canet@irqsave.net>
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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>
Cc: Chris Friesen <chris.friesen@windriver.com>, qemu-devel@nongnu.org

The Saturday 19 Jul 2014 =E0 09:23:50 (+0200), Paolo Bonzini wrote :
> Il 19/07/2014 08:27, Chris Friesen ha scritto:
> > Does it track in-flight operations though?  Or just how many operatio=
ns
> > can be requested in a given amount of time?
>=20
> It should track in flight operations.  However, I'm not sure it support=
s
> the iops=3D0 case properly, since I do not see anything in
> tracked_request_end that ceases the accounting of the current operation=
.
>  Benoit, can you answer?
>=20
> Paolo

I think in the throttling case the number of in flight operation is limit=
ed by
the emulated hardware queue. Else request would pile up and throttling wo=
uld be
inefective.

So this number should be around: #define VIRTIO_PCI_QUEUE_MAX 64 or somet=
hing like than that.

>=20
> > 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.
> >=20
> > I suppose I'll have to check the code. :)
>=20