Re: [Qemu-devel] [PATCH v7 41/42] Disable mlock around incoming postcopy

[Dr. David Alan Gilbert]

* Juan Quintela (address@hidden) wrote:
> Amit Shah <address@hidden> wrote:
> > On (Tue) 14 Jul 2015 [17:22:13], Juan Quintela wrote:
> >> "Dr. David Alan Gilbert (git)" <address@hidden> wrote:
> >
> >> > +    if (enable_mlock) {
> >> > +        if (os_mlock() < 0) {
> >> > +            error_report("mlock: %s", strerror(errno));
> >> > +            /*
> >> > +             * It doesn't feel right to fail at this point, we have a 
> >> > valid
> >> > +             * VM state.
> >> > +             */
> >> 
> >> realtime_init() exit in case of os_mlock() fails, so current code is:
> >
> > Yea, I was wondering the same - but then I thought: would the realtime
> > case want a migration to happen at all?
> 
> Then disable migration with realtime looks like saner.  But that
> decission don't belong to this series.

I added this patch because Zhanghailiang had reported trying to use it and it
failing.

Zhanghailiang: Do you have a use case for mlock=on and migration?

Dave

> 
> >
> >> - we start qemu with mlock requset
> >> - we mlock memory
> >> - we start postcopy
> >> - we munlock memory
> >> - we mlock memory
> >> 
> >> I wmill really, really preffer having a check if memory is mlocked, and
> >> it that case, just abort migration altogether.  Or better still, wait to
> >> enable mlock *until* we have finished postcopy, no?
> >
> >             Amit
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK