[Qemu-devel] [PATCH COLO-Frame v15 12/38] ram/COLO: Record the dirty pages that SVM received

[zhanghailiang <zhang.zhanghailiang@huawei.com>]

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.

Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
v12:
- Add Reviewed-by tag
v11:
- Split a new helper function from original
  host_from_stream_offset() (Dave's suggestion)
- Only do recording work in this patch
v10:
- New patch split from v9's patch 13
- Rebase to master to use 'migration_bitmap_rcu'
---
 migration/ram.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/migration/ram.c b/migration/ram.c
index 027c5bc..7373df3 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2195,6 +2195,9 @@ 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;
+
     if (!offset_in_ramblock(block, offset)) {
         return NULL;
     }
@@ -2203,6 +2206,17 @@ static inline void *colo_cache_from_block_offset(RAMBlock *block,
                      __func__, block->idstr);
         return NULL;
     }
+
+    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++;
+    }
     return block->colo_cache + offset;
 }
 
@@ -2589,6 +2603,7 @@ 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) {
@@ -2603,6 +2618,15 @@ 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:
@@ -2620,9 +2644,15 @@ 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