Re: [Qemu-devel] [PATCH 10/17] migration: create ram_multifd_page

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

* Juan Quintela (quintela@redhat.com) wrote:
> "Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
> > * Juan Quintela (quintela@redhat.com) wrote:
> >> The function still don't use multifd, but we have simplified
> >> ram_save_page, xbzrle and RDMA stuff is gone.  We have added a new
> >> counter and a new flag for this type of pages.
> >> 
> >> Signed-off-by: Juan Quintela <quintela@redhat.com>
> 
> >> --- a/migration/ram.c
> >> +++ b/migration/ram.c
> >> @@ -61,6 +61,7 @@ static uint64_t bitmap_sync_count;
> >>  #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_PAGE     0x200
> >
> > I think a similar reminder from the last iteration of this patch;
> > I think we're out of bits here - I'm not sure if 0x200 is even
> > available.
> 
> In previous iteration, I used *two* bits.  As per your recomendation, I
> "reused" and old one for doing the synchronization.

Hmm OK, but that's still the last free bit; given TARGET_PAGE_BITS 10
on 3 targets, we can't use 0x400.
I guess the next user of a new bit will need to use RAM_SAVE_FLAG_FULL
which has never really been used and that will have to be some
magic that caused another block of bits to be read.

Dave

> 
> Later, Juan.
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK