Re: [PATCH 5/5] multifd: Only sync once each full round of memory

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Jul 05, 2022 at 02:56:35PM +0100, Dr. David Alan Gilbert wrote:
> * Juan Quintela (quintela@redhat.com) wrote:
> > We need to add a new flag to mean to sync at that point.
> > Notice that we still synchronize at the end of setup and at the end of
> > complete stages.
> > 
> > Signed-off-by: Juan Quintela <quintela@redhat.com>
> > ---
> >  migration/migration.c |  2 +-
> >  migration/ram.c       | 42 ++++++++++++++++++++++++++++++------------
> >  2 files changed, 31 insertions(+), 13 deletions(-)
> > 
> > diff --git a/migration/migration.c b/migration/migration.c
> > index 3f79df0b70..6627787fc2 100644
> > --- a/migration/migration.c
> > +++ b/migration/migration.c
> > @@ -4283,7 +4283,7 @@ static Property migration_properties[] = {
> >                        DEFAULT_MIGRATE_ANNOUNCE_STEP),
> >      /* We will change to false when we introduce the new mechanism */
> >      DEFINE_PROP_BOOL("multifd-sync-each-iteration", MigrationState,
> > -                      multifd_sync_each_iteration, true),
> > +                      multifd_sync_each_iteration, false),
> >  
> >      /* Migration capabilities */
> >      DEFINE_PROP_MIG_CAP("x-xbzrle", MIGRATION_CAPABILITY_XBZRLE),
> > diff --git a/migration/ram.c b/migration/ram.c
> > index 2c7289edad..6792986565 100644
> > --- a/migration/ram.c
> > +++ b/migration/ram.c
> > @@ -81,6 +81,7 @@
> >  #define RAM_SAVE_FLAG_XBZRLE   0x40
> >  /* 0x80 is reserved in migration.h start with 0x100 next */
> >  #define RAM_SAVE_FLAG_COMPRESS_PAGE    0x100
> > +#define RAM_SAVE_FLAG_MULTIFD_SYNC     0x200
> 
> Note this is the very last usable flag!
> We could do with avoiding using them as flags where we dont need to.

Before it is too late, shouldn't we do

   #define RAM_SAVE_FLAG_BIGGER_FLAGS 0x200  

to indicate that this will be followed by another uint64 value
giving us another 64 flags to play with ?


With regards,
Daniel
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