Re: [Qemu-devel] [PATCH COLO-Frame v10 15/38] ram/COLO: Record pages received from PVM by re-using migration dirty bitmap

[Dr. David Alan Gilbert]

* zhanghailiang (address@hidden) wrote:
> We need to record the address of the dirty pages that received from PVM,
> It will help flushing pages that cached into SVM.
> 
> Signed-off-by: zhanghailiang <address@hidden>
> ---
> v10:
> - New patch split from v9's patch 13
> - Rebase to master to use 'migration_bitmap_rcu'
> ---
>  migration/ram.c | 35 +++++++++++++++++++++++++++++++++++
>  1 file changed, 35 insertions(+)
> 
> diff --git a/migration/ram.c b/migration/ram.c
> index b094dc3..70879bd 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -1448,6 +1448,18 @@ static inline void *host_from_stream_offset(QEMUFile 
> *f,
>          }
>  
>          if (ram_cache_enable) {
> +            unsigned long *bitmap;
> +            long k = (block->mr->ram_addr + 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++;
> +            }

I don't like having this in host_from_stream_offset; if you look
at the current ram_load there is only a single call to host_from_stream_offset, 
so it's
now much easier for you to move it into a separate function.

>              return block->host_cache + offset;
>          } else {
>              return block->host + offset;
> @@ -1462,6 +1474,13 @@ static inline void *host_from_stream_offset(QEMUFile 
> *f,
>          if (!strncmp(id, block->idstr, sizeof(id)) &&
>              block->max_length > offset) {
>              if (ram_cache_enable) {
> +                unsigned long *bitmap;
> +                long k = (block->mr->ram_addr + offset) >> TARGET_PAGE_BITS;
> +
> +                bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap;
> +                if (!test_and_set_bit(k, bitmap)) {
> +                    migration_dirty_pages++;
> +                }
>                  return block->host_cache + offset;
>              } else {
>                  return block->host + offset;
> @@ -1723,6 +1742,7 @@ 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) {
> @@ -1734,6 +1754,15 @@ 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_new(struct BitmapRcu, 1);

Please update that to g_new0 (I changed the other use when I added postcopy).

Dave

> +    migration_bitmap_rcu->bmap = bitmap_new(ram_cache_pages);
> +    migration_dirty_pages = 0;
> +
>      return 0;
>  
>  out_locked:
> @@ -1751,9 +1780,15 @@ 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->host_cache) {
> -- 
> 1.8.3.1
> 
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK