Re: [PATCH V3] libxl: Increase device model startup timeout to 1min.

[Dario Faggioli <dario.faggioli@citrix.com>]

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On Tue, 2015-07-14 at 08:55 +0100, Ian Campbell wrote:
> On Tue, 2015-07-14 at 07:17 +0100, Jan Beulich wrote:
> > >>> On 07.07.15 at 17:41, <ian.campbell@citrix.com> wrote:
> > > On Tue, 2015-07-07 at 16:14 +0100, Ian Jackson wrote:
> > >> Anthony PERARD writes ("[PATCH V3] libxl: Increase device model startup 
> > > timeout to 1min."):
> > >> > On a busy host, QEMU may take more than 10s to load and start.
> > >> > 
> > >> > This is likely due to a bug in Linux where the I/O subsystem sometime
> > >> > produce high latency under load and result in QEMU taking a long time to
> > >> > load every single dynamic libraries.
> > >> 
> > >> Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
> > > 
> > > Applied.
> > 
> > So is this the "answer" to "Problems with merlot* AMD Opteron 6376
> > systems"?
> 
> It'll be hard to say until this change gets through the Xen push gate
> and that version gets used for other branches (linux testing, libvirt,
> ovmf, osstest's own gate etc).
> 
Indeed. My opinion is that no, it is not.

My understanding of the data Anthony provided is that, under some
(difficult to track/analyze/reproduce/etc) load conditions, the Linux IO
and VM subsystem suffer from high latency, delaying QEMU startup.

In the merlot* cases, the system is completely idle, apart from the
failing creation/migration operation.

So, no, I don't think that would not be the fix we need for that
situation.

> At the moment it looks like it has helped with some but not all of the
> issues.
> 
> These:
> 
> http://logs.test-lab.xenproject.org/osstest/results/host/merlot0.html
> http://logs.test-lab.xenproject.org/osstest/results/host/merlot1.html
> 
Can I ask why (I mean, e.g., comparing what with what) you're saying it
seems to have helped?

Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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