Re: [Xen-users] xl create bug on first-attempt with passthrough

[Casey DeLorme <cdelorme@xxxxxxxxx>]

Sorry, thought I hit reply all, this time making sure I do it right.

I have two guesses as to what is happening here.

First is that, for some reason, dom0 is too slow to balloon down and xl
has failed to notice this somehow. By the time you run your second
domain domain 0 has caught up.

The other option is that perhaps xl is underestimating the RAM required
to start the domain (perhaps passthrough adds some additional memory
overhead which it doesn't correctly account for) but by making room for
this first domain it inadvertently adds enough slack to the system that
a starting the second time succeeds. If this is the case then there is a
second order bug here which is that xl didn't balloon backup after the
initial domain create failed.

You are probably right, I changed some equipment and went from 6GB of RAM and 3 devices to 8GB of RAM and 4 devices.  I tried dropping it to 4GB but that didn't seem to solve the problem either.

Either way this sounds like a bug in xl's autoballooning code, it would
be useful to report as such on xen-devel.

Should I forward this response to the xen-devel list, or just create a brand new message?

 

One obvious solution/workaround would be to use the dom0_mem option and
disable auto ballooning.

I will give this a try after work today and report back.

Thanks very much for your help and advice on this.

~Casey

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