Re: [Qemu-devel] [PATCH 5/6] save_block_hdr: we can recalculate the cont parameter here

[Li, Liang Z]

> -----Original Message-----
> From: Juan Quintela [mailto:address@hidden
> Sent: Friday, February 13, 2015 6:03 AM
> To: address@hidden
> Cc: Li, Liang Z
> Subject: [PATCH 5/6] save_block_hdr: we can recalculate the cont parameter
> here
> 
> No need to pass it through all the callers.  Once there, update
> last_sent_block here.
> 
> Signed-off-by: Juan Quintela <address@hidden>
> ---
>  arch_init.c | 47 ++++++++++++++++++++++++-----------------------
>  1 file changed, 24 insertions(+), 23 deletions(-)
> 
> diff --git a/arch_init.c b/arch_init.c
> index 834f40c..95a61e2 100644
> --- a/arch_init.c
> +++ b/arch_init.c
> @@ -304,34 +304,39 @@ uint64_t xbzrle_mig_pages_overflow(void)
>      return acct_info.xbzrle_overflows;
>  }
> 
> +/* This is the last block that we have visited serching for dirty pages
> +*/ static RAMBlock *last_seen_block;
> +/* This is the last block from where we have sent data */ static
> +RAMBlock *last_sent_block; static ram_addr_t last_offset; static
> +unsigned long *migration_bitmap; static uint64_t migration_dirty_pages;
> +static uint32_t last_version; static bool ram_bulk_stage;
> +
>  static size_t save_block_hdr(QEMUFile *f, RAMBlock *block, ram_addr_t
> offset,
> -                             int cont, int flag)
> +                             int flag)
>  {
>      size_t size;
> 
> -    qemu_put_be64(f, offset | cont | flag);
> +    if (block == last_sent_block) {
> +        offset |= RAM_SAVE_FLAG_CONTINUE;
> +    }
> +
> +    qemu_put_be64(f, offset | flag);
>      size = 8;
> 
> -    if (!cont) {
> +    if (block != last_sent_block) {
>          qemu_put_byte(f, strlen(block->idstr));
>          qemu_put_buffer(f, (uint8_t *)block->idstr,
>                          strlen(block->idstr));
>          size += 1 + strlen(block->idstr);
> +        last_sent_block = block;
>      }
>      return size;
>  }

If save_block_hdr function is changed to this, then in my patch, it can't not 
be directly reused in 
compression thread. A lock is needed to access last_sent_block. I prefer the 
original implementation.

Liang