Re: [Qemu-discuss] [Qemu-devel] iolimits for virtio-9p

[Stefan Hajnoczi]

On Tue, Apr 19, 2016 at 02:09:24PM +0200, Pradeep Kiruvale wrote:
> We are planning to implement the io-limits for the virtio-9p driver i.e for
> fsdev devices.
> So, I am looking into the code base and how it has done for the block io
> devices.
> 
> I would like to know how difficult is this and is there some one out there
> who has any plan to do this?

CCing Alberto Garcia, QEMU I/O throttling maintainer.

Take a look at include/qemu/throttle.h.  That is the common throttling
API.

Stefan


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Re: [Qemu-discuss] iolimits for virtio-9p

[Alberto Garcia]

On Tue 19 Apr 2016 02:09:24 PM CEST, Pradeep Kiruvale wrote:

> We are planning to implement the io-limits for the virtio-9p driver
> i.e for fsdev devices.
> So, I am looking into the code base and how it has done for the block
> io devices.
>
> I would like to know how difficult is this and is there some one out
> there who has any plan to do this?

Hi,

as Stefan said already, the common API is in throttle.h.

It should be generic enough to be used in other parts of QEMU, but tell
me if you feel that it needs changes.

Once you configure the throttling settings you essentially only need to
call throttle_schedule_timer() to see if a request needs to be
throttled, and afterwards throttle_account() to register the I/O that
has been peformed.

You'll see that there's also throttle-group.c, but that's specific to
the block layer and not meant to be generic.

Berto

Re: [Qemu-discuss] [Qemu-devel] iolimits for virtio-9p

[Pradeep Kiruvale]

Hi Stefan,

Thanks for the reply and adding Alberto.

I am going through those APIs already.

Thanks & Regards,
Pradeep

On 26 April 2016 at 11:21, Stefan Hajnoczi  wrote:

> On Tue, Apr 19, 2016 at 02:09:24PM +0200, Pradeep Kiruvale wrote:
> > We are planning to implement the io-limits for the virtio-9p driver i.e
> for
> > fsdev devices.
> > So, I am looking into the code base and how it has done for the block io
> > devices.
> >
> > I would like to know how difficult is this and is there some one out
> there
> > who has any plan to do this?
>
> CCing Alberto Garcia, QEMU I/O throttling maintainer.
>
> Take a look at include/qemu/throttle.h.  That is the common throttling
> API.
>
> Stefan
>

[Qemu-discuss] libvirt/virt manager: vm create -> host crash

[Alexander Petrenz]

Hello,

I would like to understand why creating a vm via libvirt crashes my host
machine. I´m configuring the new VM (e.g. in virt manager) and at the end
of the dialog I cannot directly just save it, but I need to boot it for
starting the installation.
At this point the host gradually[1] crashes. I already did some
investigation on this and one thing I realized was that libvirt needs some
firewall backend present. I don´t have any firewall configured, but I don´t
know if that is the reason.
Furthermore for performance reason I´m using hugepages for the VMs. The
host has 16gb memory and 8gb are reserved by hugepages, which leaves
another 8gb for the host. Could it be that when I configure a VM with 8gb
that it trys to allocate the 8gb and this crashes the host? As far as I
know, I cannot configure the the VM to use hugepages via the virt manager
gui, so I would have to do that later via virsh. Besides I´m not using any
swap partition.

So what could cause those host crashes? Is it all because of the memory
issue, or could the firewall issue also be the root cause?

Thanks in advance
Alex

[1]: It doesn´t freeze instantly; I can move the windows, but performing
any actions shows that nothing can be done and eventually I need to restart
it by force.