Re: [Qemu-devel] [v4 09/13] migration: Make compression co-work with xbzrle

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

* Liang Li (liang.z.li@intel.com) wrote:
> Now, multiple thread compression can co-work with xbzrle. when
> xbzrle is on, multiple thread compression will only work at the
> first round of RAM data sync.
> 
> Signed-off-by: Liang Li <liang.z.li@intel.com>
> Signed-off-by: Yang Zhang <yang.z.zhang@intel.com>
> ---
>  arch_init.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/arch_init.c b/arch_init.c
> index b8bdb16..8ef0315 100644
> --- a/arch_init.c
> +++ b/arch_init.c
> @@ -364,6 +364,7 @@ static QemuCond *comp_done_cond;
>  /* The empty QEMUFileOps will be used by file in CompressParam */
>  static const QEMUFileOps empty_ops = { };
>  static bool quit_thread;
> +static bool compression_switch_on;


Yes, OK; a bit of an odd name, but I can see what it's trying to do.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

>  static int one_byte_count;
>  static DecompressParam *decomp_param;
>  static QemuThread *decompress_threads;
> @@ -440,6 +441,7 @@ void migrate_compress_threads_create(MigrationState *s)
>          return;
>      }
>      quit_thread = false;
> +    compression_switch_on = true;
>      thread_count = migrate_compress_threads();
>      s->compress_thread = g_new0(QemuThread, thread_count);
>      comp_param = g_new0(CompressParam, thread_count);
> @@ -957,9 +959,16 @@ static int ram_find_and_save_block(QEMUFile *f, bool last_stage)
>                  block = QTAILQ_FIRST(&ram_list.blocks);
>                  complete_round = true;
>                  ram_bulk_stage = false;
> +                if (migrate_use_xbzrle()) {
> +                    /* If xbzrle is on, stop using the data compression at this
> +                     * point. In theory, xbzrle can do better than compression.
> +                     */
> +                    flush_compressed_data(f);
> +                    compression_switch_on = false;
> +                }
>              }
>          } else {
> -            if (migrate_use_compression()) {
> +            if (compression_switch_on && migrate_use_compression()) {
>                  bytes_sent = ram_save_compressed_page(f, block, offset,
>                                                        last_stage);
>              } else {
> -- 
> 1.9.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK