Re: [Xen-devel] save & restore failed when tmem enabled in Xen 4.1 & Xen 4.3

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, Jun 04, 2015 at 10:27:06PM +0800, yunfang tai wrote:
> Hi all,

Hey!
>     Recently, I am testing the TMEM support on Xen. I discovered that when
> enabled TMEM in ubuntu 14.10 as guest on Xen 4.1 & Xen 4.3, "xm save" & "xm
> restoreâ failed after there are more than 1000 pages put in persistent pool
> of TMEM in Xen. My operations are list as follows:

Is it exactly 1000 or just about? I presume it does not matter how much but
that you discovered it by having 1000 of them?

> 
> In ubuntu guest (8 cores , 8GB):
> sudo modprobe tmem
> (than wait for the selfballoon to finish)
> dd if=/dev/zero of=/tmp/test.img bs=10M count=1000
> dd if=/tmp/test.img of=/dev/null bs=10M
> dd if=/tmp/test.img of=/dev/null bs=10M
> .........
> (until more than 1000 pages put in persistent pool)

> 
> In Domain 0:
> (add tmem in grub.cfg)
> xm save ubuntu test.save
> xm restore ubuntu test.save
> 
> When TMEM is not enabled, save & restore success after these operations.
> But if TMEM is enabled, save & restore fail.

Are there any errors from the logs? Anything?
> 
> Does anyone test about save & restore when enabled TMEM in Xen?? Is there
> anything I do wrong?

Well lets see what broke. But I think Andrew discovered that the
migration protocol when it came to 'tmem' was not up to snuff. CC-ing him
just to confirm.

(Andrew, for the persistent part of this - it conceptually should
get all of the tmem memory that pushed to the hypervisor back in the
image. When you were looking at migrationv2 did you just skim through
that or mostly ignored it?)

Thanks.
> Thanks!!
> 
> Best Regards,
> Yunfang

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