Re: [Qemu-devel] [PATCH v4 45/47] Start up a postcopy/listener thread ready for incoming page data

[Dr. David Alan Gilbert]

* David Gibson (address@hidden) wrote:
> On Wed, Nov 19, 2014 at 07:40:20PM +0000, Dr. David Alan Gilbert wrote:
> > * David Gibson (address@hidden) wrote:
> > > On Fri, Oct 03, 2014 at 06:47:51PM +0100, Dr. David Alan Gilbert (git) 
> > > wrote:
> > > > From: "Dr. David Alan Gilbert" <address@hidden>
> > > > 
> > > > The loading of a device state (during postcopy) may access guest
> > > > memory that's still on the source machine and thus might need
> > > > a page fill; split off a separate thread that handles the incoming
> > > > page data so that the original incoming migration code can finish
> > > > off the device data.
> > > > 
> > > > Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> > > > ---
> > > >  include/migration/migration.h |  4 +++
> > > >  migration.c                   |  6 +++++
> > > >  savevm.c                      | 62 
> > > > +++++++++++++++++++++++++++++++++++++++++--
> > > >  3 files changed, 70 insertions(+), 2 deletions(-)
> > > > 
> > > > diff --git a/include/migration/migration.h 
> > > > b/include/migration/migration.h
> > > > index 00255b8..69e776c 100644
> > > > --- a/include/migration/migration.h
> > > > +++ b/include/migration/migration.h
> > > > @@ -92,6 +92,10 @@ struct MigrationIncomingState {
> > > >      QemuThread     fault_thread;
> > > >      QemuSemaphore  fault_thread_sem;
> > > >  
> > > > +    bool           have_listen_thread;
> > > 
> > > AFAICT have_listen_thread is never set to a value other than 'true',
> > > so there doesn't see much point to it.
> > 
> > It's tested by qemu_loadvm_state to avoid doing cleaning stuff up as it 
> > exits,
> > since the listen thread is still using it.
> 
> Right, but I couldn't see under what circumstances it would ever be
> false at the test false in qemu_loadvm_state().

In a normal pre-copy case where we don't have a listen-thread.

Dave

> 
> -- 
> David Gibson                  | I'll have my music baroque, and my code
> david AT gibson.dropbear.id.au        | minimalist, thank you.  NOT _the_ 
> _other_
>                               | _way_ _around_!
> http://www.ozlabs.org/~dgibson


--
Dr. David Alan Gilbert / address@hidden / Manchester, UK