[PATCH RFC 01/10] migration: Introduce structs for periodic CPU throttle

[Hyman Huang]

shadow_bmap, iter_bmap, iter_dirty_pages and
periodic_sync_shown_up are introduced to satisfy the need
for periodic CPU throttle.

Meanwhile, introduce enumeration of dirty bitmap sync method.

Signed-off-by: Hyman Huang <yong.hu...@smartx.com>
---
 include/exec/ramblock.h | 45 +++++++++++++++++++++++++++++++++++++++++
 migration/ram.c         |  6 ++++++
 2 files changed, 51 insertions(+)

diff --git a/include/exec/ramblock.h b/include/exec/ramblock.h
index 0babd105c0..619c52885a 100644
--- a/include/exec/ramblock.h
+++ b/include/exec/ramblock.h
@@ -24,6 +24,30 @@
 #include "qemu/rcu.h"
 #include "exec/ramlist.h"
 
+/* Possible bits for migration_bitmap_sync */
+
+/*
+ * The old-fashioned sync method, which is, in turn, used for CPU
+ * throttle and memory transfer.
+ */
+#define RAMBLOCK_SYN_LEGACY_ITER    (1U << 0)
+
+/*
+ * The modern sync method, which is, in turn, used for CPU throttle
+ * and memory transfer.
+ */
+#define RAMBLOCK_SYN_MODERN_ITER    (1U << 1)
+
+/* The modern sync method, which is used for CPU throttle only */
+#define RAMBLOCK_SYN_MODERN_PERIOD  (1U << 2)
+
+#define RAMBLOCK_SYN_MASK   (0x7)
+
+typedef enum RAMBlockSynMode {
+    RAMBLOCK_SYN_LEGACY,    /* Old-fashined mode */
+    RAMBLOCK_SYN_MODERN,
+} RAMBlockSynMode;
+
 struct RAMBlock {
     struct rcu_head rcu;
     struct MemoryRegion *mr;
@@ -89,6 +113,27 @@ struct RAMBlock {
      * could not have been valid on the source.
      */
     ram_addr_t postcopy_length;
+
+    /*
+     * Used to backup the bmap during periodic sync to see whether any dirty
+     * pages were sent during that time.
+     */
+    unsigned long *shadow_bmap;
+
+    /*
+     * The bitmap "bmap," which was initially used for both sync and memory
+     * transfer, will be replaced by two bitmaps: the previously used "bmap"
+     * and the recently added "iter_bmap." Only the memory transfer is
+     * conducted with the previously used "bmap"; the recently added
+     * "iter_bmap" is utilized for sync.
+     */
+    unsigned long *iter_bmap;
+
+    /* Number of new dirty pages during iteration */
+    uint64_t iter_dirty_pages;
+
+    /* If periodic sync has shown up during iteration */
+    bool periodic_sync_shown_up;
 };
 #endif
 #endif
diff --git a/migration/ram.c b/migration/ram.c
index 67ca3d5d51..f29faa82d6 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2362,6 +2362,10 @@ static void ram_bitmaps_destroy(void)
         block->bmap = NULL;
         g_free(block->file_bmap);
         block->file_bmap = NULL;
+        g_free(block->shadow_bmap);
+        block->shadow_bmap = NULL;
+        g_free(block->iter_bmap);
+        block->iter_bmap = NULL;
     }
 }
 
@@ -2753,6 +2757,8 @@ static void ram_list_init_bitmaps(void)
             }
             block->clear_bmap_shift = shift;
             block->clear_bmap = bitmap_new(clear_bmap_size(pages, shift));
+            block->shadow_bmap = bitmap_new(pages);
+            block->iter_bmap = bitmap_new(pages);
         }
     }
 }
-- 
2.39.1