Re: [PATCH 04/14] migration: Remove RAMState.f references in compression code

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

* Peter Xu (peterx@redhat.com) wrote:
> Removing referencing to RAMState.f in compress_page_with_multi_thread() and
> flush_compressed_data().
> 
> Compression code by default isn't compatible with having >1 channels (or it
> won't currently know which channel to flush the compressed data), so to
> make it simple we always flush on the default to_dst_file port until
> someone wants to add >1 ports support, as rs->f right now can really
> change (after postcopy preempt is introduced).
> 
> There should be no functional change at all after patch applied, since as
> long as rs->f referenced in compression code, it must be to_dst_file.
> 
> Signed-off-by: Peter Xu <peterx@redhat.com>

Yes, I think that's true - although I think we need to add checks to
stop someone trying to enable compression+multifd?



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


> ---
>  migration/ram.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/migration/ram.c b/migration/ram.c
> index 62ff2c1469..8303252b6d 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -1461,6 +1461,7 @@ static bool save_page_use_compression(RAMState *rs);
>  
>  static void flush_compressed_data(RAMState *rs)
>  {
> +    MigrationState *ms = migrate_get_current();
>      int idx, len, thread_count;
>  
>      if (!save_page_use_compression(rs)) {
> @@ -1479,7 +1480,7 @@ static void flush_compressed_data(RAMState *rs)
>      for (idx = 0; idx < thread_count; idx++) {
>          qemu_mutex_lock(&comp_param[idx].mutex);
>          if (!comp_param[idx].quit) {
> -            len = qemu_put_qemu_file(rs->f, comp_param[idx].file);
> +            len = qemu_put_qemu_file(ms->to_dst_file, comp_param[idx].file);
>              /*
>               * it's safe to fetch zero_page without holding comp_done_lock
>               * as there is no further request submitted to the thread,
> @@ -1498,11 +1499,11 @@ static inline void set_compress_params(CompressParam *param, RAMBlock *block,
>      param->offset = offset;
>  }
>  
> -static int compress_page_with_multi_thread(RAMState *rs, RAMBlock *block,
> -                                           ram_addr_t offset)
> +static int compress_page_with_multi_thread(RAMBlock *block, ram_addr_t offset)
>  {
>      int idx, thread_count, bytes_xmit = -1, pages = -1;
>      bool wait = migrate_compress_wait_thread();
> +    MigrationState *ms = migrate_get_current();
>  
>      thread_count = migrate_compress_threads();
>      qemu_mutex_lock(&comp_done_lock);
> @@ -1510,7 +1511,8 @@ retry:
>      for (idx = 0; idx < thread_count; idx++) {
>          if (comp_param[idx].done) {
>              comp_param[idx].done = false;
> -            bytes_xmit = qemu_put_qemu_file(rs->f, comp_param[idx].file);
> +            bytes_xmit = qemu_put_qemu_file(ms->to_dst_file,
> +                                            comp_param[idx].file);
>              qemu_mutex_lock(&comp_param[idx].mutex);
>              set_compress_params(&comp_param[idx], block, offset);
>              qemu_cond_signal(&comp_param[idx].cond);
> @@ -2263,7 +2265,7 @@ static bool save_compress_page(RAMState *rs, RAMBlock *block, ram_addr_t offset)
>          return false;
>      }
>  
> -    if (compress_page_with_multi_thread(rs, block, offset) > 0) {
> +    if (compress_page_with_multi_thread(block, offset) > 0) {
>          return true;
>      }
>  
> -- 
> 2.32.0
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK