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List:       kvm
Subject:    RE: migrate_set_downtime bug
From:       Dietmar Maurer <dietmar () proxmox ! com>
Date:       2009-09-30 18:41:37
Message-ID: 90D306BE6EBC8D428A824FBBA7A3113DFDCDF18E () ronja ! maurer-it ! com
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> > > > +    if ((stage == 2) && (bytes_transferred >
> 2*ram_bytes_total())) {
> > > > +        return 1;
> > > > +    }
> > > why 2 * ?
> > > This means we'll have to transfer the whole contents of RAM at
> least
> > > twice to hit this condition, right?
> > 
> > Yes, this is just an arbitrary limit.
> I don't know. If we are going for a limit, I would prefere a limit of
> pages yet to transfer,
> not pages already transferred.
> 
> However, the very reason this whole thing was written in the first
> place, was to leave choices
> to management tools ontop of qemu, not qemu itself. So I would say yes,
> if you set limit for 30ns,
> you asked for it never finishing.

I just think of common scenarios like 'maintanace mode', where all VM should migrate \
to another host. A endless migrate task can make that fail. 

For me, it is totally unclear what value I should set for 'max_downtime' to avoid \
that behavior?

- Dietmar


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