Re: [Qemu-devel] [PATCH 40/54] ram: Remove compression_switch and inline its logic

[Peter Xu]

On Thu, Apr 06, 2017 at 03:08:59PM +0200, Juan Quintela wrote:
> We can calculate its value, so not create a varible for it.
> 
> Signed-off-by: Juan Quintela <address@hidden>
> 
> --
> 
> After Peter and Dave review, I dropped the variable and just inlined
> the condition.
> 
> Later, Juan.
> 
> Signed-off-by: Juan Quintela <address@hidden>
> ---
>  migration/ram.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/migration/ram.c b/migration/ram.c
> index 14d54fd..5dfc9bd 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -336,7 +336,6 @@ static QemuCond comp_done_cond;
>  /* The empty QEMUFileOps will be used by file in CompressParam */
>  static const QEMUFileOps empty_ops = { };
>  
> -static bool compression_switch;
>  static DecompressParam *decomp_param;
>  static QemuThread *decompress_threads;
>  static QemuMutex decomp_done_lock;
> @@ -420,7 +419,6 @@ void migrate_compress_threads_create(void)
>      if (!migrate_use_compression()) {
>          return;
>      }
> -    compression_switch = true;
>      thread_count = migrate_compress_threads();
>      compress_threads = g_new0(QemuThread, thread_count);
>      comp_param = g_new0(CompressParam, thread_count);
> @@ -1092,7 +1090,6 @@ static bool find_dirty_block(RAMState *rs, 
> PageSearchStatus *pss,
>                   * point. In theory, xbzrle can do better than compression.
>                   */
>                  flush_compressed_data(rs);
> -                compression_switch = false;
>              }
>          }
>          /* Didn't find anything this time, but try again on the new block */
> @@ -1326,7 +1323,14 @@ static int ram_save_target_page(RAMState *rs, 
> MigrationState *ms,
>      /* Check the pages is dirty and if it is send it */
>      if (migration_bitmap_clear_dirty(rs, dirty_ram_abs)) {
>          unsigned long *unsentmap;
> -        if (compression_switch && migrate_use_compression()) {
> +        /*
> +         * If xbzrle is on, stop using the data compression after first
> +         * round of migration even if compression is enabled. In theory,
> +         * xbzrle can do better than compression.
> +         */
> +
> +        if (migrate_use_compression())
                                        ^ is this a superfluous ")"?

> +            && (rs->ram_bulk_stage || !migrate_use_xbzrle()) {
>              res = ram_save_compressed_page(rs, ms, pss, last_stage);
>          } else {
>              res = ram_save_page(rs, ms, pss, last_stage);
> -- 
> 2.9.3

Thanks,

-- peterx