Re: [RFC PATCH 07/17] COLO buffer: implement colo buffer as well as QEMUFileOps based on it

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

* Yang Hongyang (yanghy@cn.fujitsu.com) wrote:
> We need a buffer to store migration data.
> 
> On save side:
>   all saved data was write into colo buffer first, so that we can know
> the total size of the migration data. this can also separate the data
> transmission from colo control data, we use colo control data over
> socket fd to synchronous both side's stat.
> 
> On restore side:
>   all migration data was read into colo buffer first, then load data
> from the buffer: If network error happens while data transmission,
> the slaver can still functinal because the migration data are not yet
> loaded.

This is very similar to the QEMUSizedBuffer based QEMUFile's that Stefan Berger
wrote and that I use in both my postcopy and BER patchsets:

 http://lists.gnu.org/archive/html/qemu-devel/2014-07/msg00846.html

 (and to the similar code from Isaku Yamahata).

I think we should be able to use a shared version even if we need some changes.

> 
> Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
> ---
>  migration-colo.c | 112 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 112 insertions(+)
> 
> diff --git a/migration-colo.c b/migration-colo.c
> index d566b9d..b90d9b6 100644
> --- a/migration-colo.c
> +++ b/migration-colo.c
> @@ -11,6 +11,7 @@
>  #include "qemu/main-loop.h"
>  #include "qemu/thread.h"
>  #include "block/coroutine.h"
> +#include "qemu/error-report.h"
>  #include "migration/migration-colo.h"
>  
>  static QEMUBH *colo_bh;
> @@ -20,14 +21,122 @@ bool colo_supported(void)
>      return true;
>  }
>  
> +/* colo buffer */
> +
> +#define COLO_BUFFER_BASE_SIZE (1000*1000*4ULL)
> +#define COLO_BUFFER_MAX_SIZE (1000*1000*1000*10ULL)

Powers of 2 are nicer!

Dave
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK