Re: [Qemu-devel] [PATCH v5 20/45] Modify savevm handlers for postcopy

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* David Gibson (david@gibson.dropbear.id.au) wrote:
> On Wed, Feb 25, 2015 at 04:51:43PM +0000, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> > 
> > Modify save_live_pending to return separate postcopiable and
> > non-postcopiable counts.
> > 
> > Add 'can_postcopy' to allow a device to state if it can postcopy
> 
> What's the purpose of the can_postcopy callback?  There are no callers
> in this patch - is it still necessary with the change to
> save_live_pending?

The patch 'qemu_savevm_state_complete: Postcopy changes' uses
it in qemu_savevm_state_postcopy_complete and qemu_savevm_state_complete
to decide which devices must be completed at that point.

Dave

> 
> > 
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> >  arch_init.c                 | 15 +++++++++++++--
> >  include/migration/vmstate.h | 10 ++++++++--
> >  include/sysemu/sysemu.h     |  4 +++-
> >  migration/block.c           |  7 +++++--
> >  migration/migration.c       |  9 +++++++--
> >  savevm.c                    | 21 +++++++++++++++++----
> >  trace-events                |  2 +-
> >  7 files changed, 54 insertions(+), 14 deletions(-)
> > 
> > diff --git a/arch_init.c b/arch_init.c
> > index fe0df0d..7bc5fa6 100644
> > --- a/arch_init.c
> > +++ b/arch_init.c
> > @@ -997,7 +997,9 @@ static int ram_save_complete(QEMUFile *f, void *opaque)
> >      return 0;
> >  }
> >  
> > -static uint64_t ram_save_pending(QEMUFile *f, void *opaque, uint64_t max_size)
> > +static void ram_save_pending(QEMUFile *f, void *opaque, uint64_t max_size,
> > +                             uint64_t *non_postcopiable_pending,
> > +                             uint64_t *postcopiable_pending)
> >  {
> >      uint64_t remaining_size;
> >  
> > @@ -1009,7 +1011,9 @@ static uint64_t ram_save_pending(QEMUFile *f, void *opaque, uint64_t max_size)
> >          qemu_mutex_unlock_iothread();
> >          remaining_size = ram_save_remaining() * TARGET_PAGE_SIZE;
> >      }
> > -    return remaining_size;
> > +
> > +    *non_postcopiable_pending = 0;
> > +    *postcopiable_pending = remaining_size;
> >  }
> >  
> >  static int load_xbzrle(QEMUFile *f, ram_addr_t addr, void *host)
> > @@ -1204,6 +1208,12 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
> >      return ret;
> >  }
> >  
> > +/* RAM's always up for postcopying */
> > +static bool ram_can_postcopy(void *opaque)
> > +{
> > +    return true;
> > +}
> > +
> >  static SaveVMHandlers savevm_ram_handlers = {
> >      .save_live_setup = ram_save_setup,
> >      .save_live_iterate = ram_save_iterate,
> > @@ -1211,6 +1221,7 @@ static SaveVMHandlers savevm_ram_handlers = {
> >      .save_live_pending = ram_save_pending,
> >      .load_state = ram_load,
> >      .cancel = ram_migration_cancel,
> > +    .can_postcopy = ram_can_postcopy,
> >  };
> >  
> >  void ram_mig_init(void)
> > diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
> > index 18da207..c9ec74a 100644
> > --- a/include/migration/vmstate.h
> > +++ b/include/migration/vmstate.h
> > @@ -54,8 +54,14 @@ typedef struct SaveVMHandlers {
> >  
> >      /* This runs outside the iothread lock!  */
> >      int (*save_live_setup)(QEMUFile *f, void *opaque);
> > -    uint64_t (*save_live_pending)(QEMUFile *f, void *opaque, uint64_t max_size);
> > -
> > +    /*
> > +     * postcopiable_pending must return 0 unless the can_postcopy
> > +     * handler returns true.
> > +     */
> > +    void (*save_live_pending)(QEMUFile *f, void *opaque, uint64_t max_size,
> > +                              uint64_t *non_postcopiable_pending,
> > +                              uint64_t *postcopiable_pending);
> > +    bool (*can_postcopy)(void *opaque);
> >      LoadStateHandler *load_state;
> >  } SaveVMHandlers;
> >  
> > diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
> > index e83bf80..5f518b3 100644
> > --- a/include/sysemu/sysemu.h
> > +++ b/include/sysemu/sysemu.h
> > @@ -111,7 +111,9 @@ void qemu_savevm_state_header(QEMUFile *f);
> >  int qemu_savevm_state_iterate(QEMUFile *f);
> >  void qemu_savevm_state_complete(QEMUFile *f);
> >  void qemu_savevm_state_cancel(void);
> > -uint64_t qemu_savevm_state_pending(QEMUFile *f, uint64_t max_size);
> > +void qemu_savevm_state_pending(QEMUFile *f, uint64_t max_size,
> > +                               uint64_t *res_non_postcopiable,
> > +                               uint64_t *res_postcopiable);
> >  void qemu_savevm_command_send(QEMUFile *f, enum qemu_vm_cmd command,
> >                                uint16_t len, uint8_t *data);
> >  void qemu_savevm_send_ping(QEMUFile *f, uint32_t value);
> > diff --git a/migration/block.c b/migration/block.c
> > index 0c76106..0f6f209 100644
> > --- a/migration/block.c
> > +++ b/migration/block.c
> > @@ -754,7 +754,9 @@ static int block_save_complete(QEMUFile *f, void *opaque)
> >      return 0;
> >  }
> >  
> > -static uint64_t block_save_pending(QEMUFile *f, void *opaque, uint64_t max_size)
> > +static void block_save_pending(QEMUFile *f, void *opaque, uint64_t max_size,
> > +                               uint64_t *non_postcopiable_pending,
> > +                               uint64_t *postcopiable_pending)
> >  {
> >      /* Estimate pending number of bytes to send */
> >      uint64_t pending;
> > @@ -773,7 +775,8 @@ static uint64_t block_save_pending(QEMUFile *f, void *opaque, uint64_t max_size)
> >      qemu_mutex_unlock_iothread();
> >  
> >      DPRINTF("Enter save live pending  %" PRIu64 "\n", pending);
> > -    return pending;
> > +    *non_postcopiable_pending = pending;
> > +    *postcopiable_pending = 0;
> >  }
> >  
> >  static int block_load(QEMUFile *f, void *opaque, int version_id)
> > diff --git a/migration/migration.c b/migration/migration.c
> > index 2e6adca..a4fc7d7 100644
> > --- a/migration/migration.c
> > +++ b/migration/migration.c
> > @@ -868,8 +868,13 @@ static void *migration_thread(void *opaque)
> >          uint64_t pending_size;
> >  
> >          if (!qemu_file_rate_limit(s->file)) {
> > -            pending_size = qemu_savevm_state_pending(s->file, max_size);
> > -            trace_migrate_pending(pending_size, max_size);
> > +            uint64_t pend_post, pend_nonpost;
> > +
> > +            qemu_savevm_state_pending(s->file, max_size, &pend_nonpost,
> > +                                      &pend_post);
> > +            pending_size = pend_nonpost + pend_post;
> > +            trace_migrate_pending(pending_size, max_size,
> > +                                  pend_post, pend_nonpost);
> >              if (pending_size && pending_size >= max_size) {
> >                  qemu_savevm_state_iterate(s->file);
> >              } else {
> > diff --git a/savevm.c b/savevm.c
> > index df48ba8..e301a0a 100644
> > --- a/savevm.c
> > +++ b/savevm.c
> > @@ -944,10 +944,20 @@ void qemu_savevm_state_complete(QEMUFile *f)
> >      qemu_fflush(f);
> >  }
> >  
> > -uint64_t qemu_savevm_state_pending(QEMUFile *f, uint64_t max_size)
> > +/* Give an estimate of the amount left to be transferred,
> > + * the result is split into the amount for units that can and
> > + * for units that can't do postcopy.
> > + */
> > +void qemu_savevm_state_pending(QEMUFile *f, uint64_t max_size,
> > +                               uint64_t *res_non_postcopiable,
> > +                               uint64_t *res_postcopiable)
> >  {
> >      SaveStateEntry *se;
> > -    uint64_t ret = 0;
> > +    uint64_t tmp_non_postcopiable, tmp_postcopiable;
> > +
> > +    *res_non_postcopiable = 0;
> > +    *res_postcopiable = 0;
> > +
> >  
> >      QTAILQ_FOREACH(se, &savevm_handlers, entry) {
> >          if (!se->ops || !se->ops->save_live_pending) {
> > @@ -958,9 +968,12 @@ uint64_t qemu_savevm_state_pending(QEMUFile *f, uint64_t max_size)
> >                  continue;
> >              }
> >          }
> > -        ret += se->ops->save_live_pending(f, se->opaque, max_size);
> > +        se->ops->save_live_pending(f, se->opaque, max_size,
> > +                                   &tmp_non_postcopiable, &tmp_postcopiable);
> > +
> > +        *res_postcopiable += tmp_postcopiable;
> > +        *res_non_postcopiable += tmp_non_postcopiable;
> >      }
> > -    return ret;
> >  }
> >  
> >  void qemu_savevm_state_cancel(void)
> > diff --git a/trace-events b/trace-events
> > index cbf995c..83312b6 100644
> > --- a/trace-events
> > +++ b/trace-events
> > @@ -1400,7 +1400,7 @@ migrate_fd_cleanup(void) ""
> >  migrate_fd_cleanup_src_rp(void) ""
> >  migrate_fd_error(void) ""
> >  migrate_fd_cancel(void) ""
> > -migrate_pending(uint64_t size, uint64_t max) "pending size %" PRIu64 " max %" PRIu64
> > +migrate_pending(uint64_t size, uint64_t max, uint64_t post, uint64_t nonpost) "pending size %" PRIu64 " max %" PRIu64 " (post=%" PRIu64 " nonpost=%" PRIu64 ")"
> >  migrate_send_rp_message(int cmd, uint16_t len) "cmd=%d, len=%d"
> >  open_outgoing_return_path(void) ""
> >  open_outgoing_return_path_continue(void) ""
> 
> -- 
> 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 / dgilbert@redhat.com / Manchester, UK