[Qemu-devel] [PATCH 4/4] Try not to exceed max downtime on stage3

[Liran Schour <lirans@il.ibm.com>]

Move to stage3 only when remaining work can be done below max downtime.
To make sure the process will converge we will try only MAX_DIRTY_ITERATIONS.

Signed-off-by: Liran Schour <lirans@il.ibm.com>
---
 block-migration.c |   67 +++++++++++++++++++++++++++++++++++-----------------
 1 files changed, 45 insertions(+), 22 deletions(-)

diff --git a/block-migration.c b/block-migration.c
index 90c84b1..9ae04c4 100644
--- a/block-migration.c
+++ b/block-migration.c
@@ -17,6 +17,7 @@
 #include "qemu-queue.h"
 #include "monitor.h"
 #include "block-migration.h"
+#include "migration.h"
 #include <assert.h>
 
 #define BLOCK_SIZE (BDRV_SECTORS_PER_DIRTY_CHUNK << BDRV_SECTOR_BITS)
@@ -30,6 +31,7 @@
 #define BLOCKS_READ_CHANGE 100
 #define INITIAL_BLOCKS_READ 100
 #define MAX_DIRTY_ITERATIONS 100
+#define DISK_RATE (30 << 20) //30 MB/sec
 
 //#define DEBUG_BLK_MIGRATION
 
@@ -135,10 +137,11 @@ static void blk_mig_read_cb(void *opaque, int ret)
     blk->ret = ret;
 
     QSIMPLEQ_INSERT_TAIL(&block_mig_state.blk_list, blk, entry);
-
+    
     block_mig_state.submitted--;
     block_mig_state.read_done++;
     assert(block_mig_state.submitted >= 0);
+    
 }
 
 static int mig_save_device_bulk(Monitor *mon, QEMUFile *f,
@@ -225,7 +228,7 @@ static void init_blk_migration(Monitor *mon, QEMUFile *f)
     block_mig_state.prev_progress = -1;
     block_mig_state.bulk_completed = 0;
     block_mig_state.dirty_iterations = 0;
-
+    
     for (bs = bdrv_first; bs != NULL; bs = bs->next) {
         if (bs->type == BDRV_TYPE_HD) {
             sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
@@ -405,15 +408,41 @@ static void flush_blks(QEMUFile* f)
             block_mig_state.transferred);
 }
 
-static int is_stage2_completed(void)
+static int64_t get_remaining_dirty(void)
 {
+    BlkMigDevState *bmds;
+    int64_t dirty = 0;
+    
+    QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
+        dirty += bdrv_get_dirty_count(bmds->bs);
+    }
+    
+    return dirty;
+}
 
-    if (block_mig_state.submitted == 0 &&
-        block_mig_state.bulk_completed == 1) {
-        return 1;
-    } else {
-        return 0;
+static int is_stage2_completed(void)
+{
+    int64_t remaining_dirty;
+    
+    if (block_mig_state.bulk_completed == 1) {
+        if (block_mig_state.dirty_iterations++ > MAX_DIRTY_ITERATIONS) {
+            /* finish stage2 because we have too much dirty iterations */
+            
+            return 1;
+        }
+        
+        remaining_dirty = get_remaining_dirty();
+        
+        if ((remaining_dirty * BLOCK_SIZE) * 1000000000 / DISK_RATE <= 
+            migrate_max_downtime()) {
+            /* finish stage2 because we think that we can finish remaing work
+               below max_downtime */
+            
+            return 1;
+        }
     }
+    
+    return 0;
 }
 
 static void blk_mig_cleanup(Monitor *mon)
@@ -438,9 +467,7 @@ static void blk_mig_cleanup(Monitor *mon)
 }
 
 static int block_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
-{
-    int dirty_iteration = 0;
-    
+{    
     dprintf("Enter save live stage %d submitted %d transferred %d\n",
             stage, block_mig_state.submitted, block_mig_state.transferred);
 
@@ -482,19 +509,12 @@ static int block_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
                     /* finish saving bulk on all devices */
                     block_mig_state.bulk_completed = 1;
                 }
-            } else if (block_mig_state.dirty_iterations < MAX_DIRTY_ITERATIONS) {
-                if (dirty_iteration == 0) {
-                    /* increment dirty iteration only once per round */
-                    dirty_iteration = 1;
-                    block_mig_state.dirty_iterations++;
-                }
+            } else {
+                
                 if (blk_mig_save_dirty_block(mon, f, 1) == 0) {
                     /* no more dirty blocks */
                     break;
                 }
-            } else {
-                /* if we got here stop the loop */
-                break;
             }
         }
         
@@ -507,9 +527,12 @@ static int block_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
     }
     
     if (stage == 3) {
-        /* we now for sure that save bulk is completed */
-
+        /* we know for sure that save bulk is completed and
+           all async read completed */
+        assert(block_mig_state.submitted == 0);
+        
         while(blk_mig_save_dirty_block(mon, f, 0) != 0);
+        
         blk_mig_cleanup(mon);
 
         /* report completion */
-- 
1.5.2.4