Re: [Qemu-devel] [PATCH 13/18] arch_init: adjust ram_save_setup() for migrate_is_localhost

[Lei Li]

On 08/21/2013 06:48 PM, Paolo Bonzini wrote:
> Il 21/08/2013 09:18, Lei Li ha scritto:
> > Send all the ram blocks hooked by save_page, which will copy
> > ram page and MADV_DONTNEED the page just copied.
> You should implement this entirely in the hook.
>
> It will be a little less efficient because of the dirty bitmap overhead,
> but you should aim at having *zero* changes in arch_init.c and migration.c.

Yes, the reason I modify the migration_thread() to have new process that send 
all
the ram pages in adjusted qemu_savevm_state_begin stage and send device states 
in
qemu_savevm_device_state stage for localhost migration is to avoid the bitmap 
thing,
which is a little less efficient just like you mentioned above.

The performance assurance is very important to this feature, our goal is 100ms
of downtime for a 1TB guest.

> Paolo
>
> > Signed-off-by: Lei Li <address@hidden>
> > ---
> >   arch_init.c |   19 +++++++++++++------
> >   1 files changed, 13 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch_init.c b/arch_init.c
> > index 434a4ca..cbbb4db 100644
> > --- a/arch_init.c
> > +++ b/arch_init.c
> > @@ -474,7 +474,7 @@ static int ram_save_block(QEMUFile *f, bool last_stage)
> >               /* In doubt sent page as normal */
> >               bytes_sent = -1;
> >               ret = ram_control_save_page(f, block->offset,
> > -                               offset, TARGET_PAGE_SIZE, &bytes_sent);
> > +                                        offset, TARGET_PAGE_SIZE, &bytes_sent);
> >   
> >               if (ret != RAM_SAVE_CONTROL_NOT_SUPP) {
> >                   if (ret != RAM_SAVE_CONTROL_DELAYED) {
> > @@ -613,11 +613,13 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
> >       RAMBlock *block;
> >       int64_t ram_pages = last_ram_offset() >> TARGET_PAGE_BITS;
> >   
> > -    migration_bitmap = bitmap_new(ram_pages);
> > -    bitmap_set(migration_bitmap, 0, ram_pages);
> > -    migration_dirty_pages = ram_pages;
> > -    mig_throttle_on = false;
> > -    dirty_rate_high_cnt = 0;
> > +    if (!migrate_is_localhost()) {
> > +        migration_bitmap = bitmap_new(ram_pages);
> > +        bitmap_set(migration_bitmap, 0, ram_pages);
> > +        migration_dirty_pages = ram_pages;
> > +        mig_throttle_on = false;
> > +        dirty_rate_high_cnt = 0;
> > +    }
> >   
> >       if (migrate_use_xbzrle()) {
> >           XBZRLE.cache = cache_init(migrate_xbzrle_cache_size() /
> > @@ -641,6 +643,11 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
> >       migration_bitmap_sync();
> >       qemu_mutex_unlock_iothread();
> >   
> > +    if (migrate_is_localhost()) {
> > +        ram_save_blocks(f);
> > +        return 0;
> > +    }
> > +
> >       qemu_put_be64(f, ram_bytes_total() | RAM_SAVE_FLAG_MEM_SIZE);
> >   
> >       QTAILQ_FOREACH(block, &ram_list.blocks, next) {


--
Lei