Re: [Qemu-devel] [RFC v2 25/33] migration: setup ramstate for resume

[Dr. David Alan Gilbert]

* Peter Xu (address@hidden) wrote:
> After we updated the dirty bitmaps of ramblocks, we also need to update
> the critical fields in RAMState to make sure it is ready for a resume.
> 
> Signed-off-by: Peter Xu <address@hidden>
> ---
>  migration/ram.c        | 37 ++++++++++++++++++++++++++++++++++++-
>  migration/trace-events |  1 +
>  2 files changed, 37 insertions(+), 1 deletion(-)
> 
> diff --git a/migration/ram.c b/migration/ram.c
> index afabcf5..c5d9028 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -1986,6 +1986,33 @@ static int ram_state_init(RAMState **rsp)
>      return 0;
>  }
>  
> +static void ram_state_resume_prepare(RAMState *rs)
> +{
> +    RAMBlock *block;
> +    long pages = 0;
> +
> +    /*
> +     * Postcopy is not using xbzrle/compression, so no need for that.
> +     * Also, since source are already halted, we don't need to care
> +     * about dirty page logging as well.
> +     */
> +
> +    RAMBLOCK_FOREACH(block) {
> +        pages += bitmap_count_one(block->bmap,
> +                                  block->used_length >> TARGET_PAGE_BITS);
> +    }
> +
> +    /* This may not be aligned with current bitmaps. Recalculate. */
> +    rs->migration_dirty_pages = pages;
> +
> +    rs->last_seen_block = NULL;
> +    rs->last_sent_block = NULL;
> +    rs->last_page = 0;
> +    rs->last_version = ram_list.version;
> +
> +    trace_ram_state_resume_prepare(pages);

Yes, I think this is fine;  I wonder what happens if pages is 0?
However,


Reviewed-by: Dr. David Alan Gilbert <address@hidden>

> +}
> +
>  /*
>   * Each of ram_save_setup, ram_save_iterate and ram_save_complete has
>   * long-running RCU critical section.  When rcu-reclaims in the code
> @@ -2909,8 +2936,16 @@ out:
>  static int ram_resume_prepare(MigrationState *s, void *opaque)
>  {
>      RAMState *rs = *(RAMState **)opaque;
> +    int ret;
>  
> -    return ram_dirty_bitmap_sync_all(s, rs);
> +    ret = ram_dirty_bitmap_sync_all(s, rs);
> +    if (ret) {
> +        return ret;
> +    }
> +
> +    ram_state_resume_prepare(rs);
> +
> +    return 0;
>  }
>  
>  static SaveVMHandlers savevm_ram_handlers = {
> diff --git a/migration/trace-events b/migration/trace-events
> index 8962916..6e06283 100644
> --- a/migration/trace-events
> +++ b/migration/trace-events
> @@ -85,6 +85,7 @@ ram_dirty_bitmap_sync_start(void) ""
>  ram_dirty_bitmap_sync_wait(void) ""
>  ram_dirty_bitmap_sync_notify(void) ""
>  ram_dirty_bitmap_sync_complete(void) ""
> +ram_state_resume_prepare(long v) "%ld"
>  
>  # migration/migration.c
>  await_return_path_close_on_source_close(void) ""
> -- 
> 2.7.4
> 
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK