Re: [Qemu-devel] [PATCH 08/15] ram/COLO: Record the dirty pages that SVM received

[Dr. David Alan Gilbert]

* zhanghailiang (address@hidden) wrote:
> We record the address of the dirty pages that received,
> it will help flushing pages that cached into SVM.
> We record them by re-using migration dirty bitmap.
> 
> Cc: Juan Quintela <address@hidden>
> Signed-off-by: zhanghailiang <address@hidden>
> Reviewed-by: Dr. David Alan Gilbert <address@hidden>
> ---
>  migration/ram.c | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
> 
> diff --git a/migration/ram.c b/migration/ram.c
> index b588990..ed3b606 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -2231,6 +2231,9 @@ static inline void *host_from_ram_block_offset(RAMBlock 
> *block,
>  static inline void *colo_cache_from_block_offset(RAMBlock *block,
>                                                   ram_addr_t offset)
>  {
> +    unsigned long *bitmap;
> +    long k;

You could use a better name than 'k'.

Dave

>      if (!offset_in_ramblock(block, offset)) {
>          return NULL;
>      }
> @@ -2239,6 +2242,17 @@ static inline void 
> *colo_cache_from_block_offset(RAMBlock *block,
>                       __func__, block->idstr);
>          return NULL;
>      }
> +
> +    k = (memory_region_get_ram_addr(block->mr) + offset) >> TARGET_PAGE_BITS;
> +    bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap;
> +    /*
> +    * During colo checkpoint, we need bitmap of these migrated pages.
> +    * It help us to decide which pages in ram cache should be flushed
> +    * into VM's RAM later.
> +    */
> +    if (!test_and_set_bit(k, bitmap)) {
> +        migration_dirty_pages++;
> +    }
>      return block->colo_cache + offset;
>  }
>  
> @@ -2664,6 +2678,7 @@ static int ram_load(QEMUFile *f, void *opaque, int 
> version_id)
>  int colo_init_ram_cache(void)
>  {
>      RAMBlock *block;
> +    int64_t ram_cache_pages = last_ram_offset() >> TARGET_PAGE_BITS;
>  
>      rcu_read_lock();
>      QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
> @@ -2678,6 +2693,15 @@ int colo_init_ram_cache(void)
>      }
>      rcu_read_unlock();
>      ram_cache_enable = true;
> +    /*
> +    * Record the dirty pages that sent by PVM, we use this dirty bitmap 
> together
> +    * with to decide which page in cache should be flushed into SVM's RAM. 
> Here
> +    * we use the same name 'migration_bitmap_rcu' as for migration.
> +    */
> +    migration_bitmap_rcu = g_new0(struct BitmapRcu, 1);
> +    migration_bitmap_rcu->bmap = bitmap_new(ram_cache_pages);
> +    migration_dirty_pages = 0;
> +
>      return 0;
>  
>  out_locked:
> @@ -2695,9 +2719,15 @@ out_locked:
>  void colo_release_ram_cache(void)
>  {
>      RAMBlock *block;
> +    struct BitmapRcu *bitmap = migration_bitmap_rcu;
>  
>      ram_cache_enable = false;
>  
> +    atomic_rcu_set(&migration_bitmap_rcu, NULL);
> +    if (bitmap) {
> +        call_rcu(bitmap, migration_bitmap_free, rcu);
> +    }
> +
>      rcu_read_lock();
>      QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
>          if (block->colo_cache) {
> -- 
> 1.8.3.1
> 
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK