Re: [Qemu-devel] [PATCH 37/51] ram: Move compression_switch to RAMState

[Juan Quintela]

"Dr. David Alan Gilbert" <address@hidden> wrote:
> * Juan Quintela (address@hidden) wrote:
>> Rename it to preffer_xbzrle that is a more descriptive name.
>> 
>> Signed-off-by: Juan Quintela <address@hidden>
>> ---
>>  migration/ram.c | 9 +++++----
>>  1 file changed, 5 insertions(+), 4 deletions(-)
>> 
>> diff --git a/migration/ram.c b/migration/ram.c
>> index 6a39704..591cf89 100644
>> --- a/migration/ram.c
>> +++ b/migration/ram.c
>> @@ -217,6 +217,9 @@ struct RAMState {
>>      uint64_t dirty_pages_rate;
>>      /* Count of requests incoming from destination */
>>      uint64_t postcopy_requests;
>> +    /* Should we move to xbzrle after the 1st round
>> +       of compression */
>> +    bool preffer_xbzrle;
>
> That's 'prefer' - however, do we need it at all?
> How about just replacing it by:
>    !ram_bulk_stage && migrate_use_xbzrle()
>
> would that work?

        if (migrate_use_compression()) &&
            (rs->ram_bulk_stage || !migrate_use_xbzrle()) {
            res = ram_save_compressed_page(rs, ms, pss, last_stage);

To remove the two !(!...)  I changed to this.

Later, Juan.


>
> Dave
>
>>      /* protects modification of the bitmap */
>>      QemuMutex bitmap_mutex;
>>      /* Ram Bitmap protected by RCU */
>> @@ -335,7 +338,6 @@ 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;
>> @@ -419,7 +421,6 @@ 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);
>> @@ -1091,7 +1092,7 @@ 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;
>> +                rs->preffer_xbzrle = true;
>>              }
>>          }
>>          /* Didn't find anything this time, but try again on the new block */
>> @@ -1323,7 +1324,7 @@ 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 (!rs->preffer_xbzrle && migrate_use_compression()) {
>>              res = ram_save_compressed_page(rs, ms, pss, last_stage);
>>          } else {
>>              res = ram_save_page(rs, ms, pss, last_stage);
>> -- 
>> 2.9.3
>> 
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK