[Qemu-devel] [PATCH COLO-Frame v15 29/38] COLO: Separate the process of saving/loading ram and device state

[zhanghailiang]

We separate the process of saving/loading ram and device state when do
checkpoint, we add new helpers for save/load ram/device. With this change,
we can directly transfer ram from master to slave without using
QEMUSizeBufferas as assistant, which also reduce the size of extra memory
been used during checkpoint.

Besides, we move the colo_flush_ram_cache to the proper position after the
above change.

Signed-off-by: zhanghailiang <address@hidden>
Signed-off-by: Li Zhijian <address@hidden>
---
v14:
- split two new patches from this patch
- Some minor fixes from Dave
v13:
- Re-use some existed helper functions to realize saving/loading
  ram and device.
v11:
- Remove load configuration section in qemu_loadvm_state_begin()
---
 migration/colo.c   | 48 ++++++++++++++++++++++++++++++++++++++----------
 migration/ram.c    |  5 -----
 migration/savevm.c |  5 +++++
 3 files changed, 43 insertions(+), 15 deletions(-)

diff --git a/migration/colo.c b/migration/colo.c
index 16bada6..300fa54 100644
--- a/migration/colo.c
+++ b/migration/colo.c
@@ -288,21 +288,37 @@ static int colo_do_checkpoint_transaction(MigrationState 
*s,
         goto out;
     }
 
+    colo_put_cmd(s->to_dst_file, COLO_MESSAGE_VMSTATE_SEND, &local_err);
+    if (local_err) {
+        goto out;
+    }
+
     /* Disable block migration */
     s->params.blk = 0;
     s->params.shared = 0;
-    qemu_savevm_state_header(trans);
-    qemu_savevm_state_begin(trans, &s->params);
+    qemu_savevm_state_begin(s->to_dst_file, &s->params);
+    ret = qemu_file_get_error(s->to_dst_file);
+    if (ret < 0) {
+        error_report("Save vm state begin error");
+        goto out;
+    }
+
     qemu_mutex_lock_iothread();
-    qemu_savevm_state_complete_precopy(trans, false);
+    /*
+    * Only save VM's live state, which not including device state.
+    * TODO: We may need a timeout mechanism to prevent COLO process
+    * to be blocked here.
+    */
+    qemu_savevm_live_state(s->to_dst_file);
+    /* Note: device state is saved into buffer */
+    ret = qemu_save_device_state(trans);
     qemu_mutex_unlock_iothread();
-
-    qemu_fflush(trans);
-
-    colo_put_cmd(s->to_dst_file, COLO_MESSAGE_VMSTATE_SEND, &local_err);
-    if (local_err) {
+    if (ret < 0) {
+        error_report("Save device state error");
         goto out;
     }
+    qemu_fflush(trans);
+
     /* we send the total size of the vmstate first */
     size = qsb_get_length(buffer);
     colo_put_cmd_value(s->to_dst_file, COLO_MESSAGE_VMSTATE_SIZE,
@@ -573,6 +589,16 @@ void *colo_process_incoming_thread(void *opaque)
             goto out;
         }
 
+        ret = qemu_loadvm_state_begin(mis->from_src_file);
+        if (ret < 0) {
+            error_report("Load vm state begin error, ret=%d", ret);
+            goto out;
+        }
+        ret = qemu_loadvm_state_main(mis->from_src_file, mis);
+        if (ret < 0) {
+            error_report("Load VM's live state (ram) error");
+            goto out;
+        }
         /* read the VM state total size first */
         value = colo_get_cmd_value(mis->from_src_file,
                                  COLO_MESSAGE_VMSTATE_SIZE, &local_err);
@@ -605,8 +631,10 @@ void *colo_process_incoming_thread(void *opaque)
         qemu_mutex_lock_iothread();
         qemu_system_reset(VMRESET_SILENT);
         vmstate_loading = true;
-        if (qemu_loadvm_state(fb) < 0) {
-            error_report("COLO: loadvm failed");
+        colo_flush_ram_cache();
+        ret = qemu_load_device_state(fb);
+        if (ret < 0) {
+            error_report("COLO: load device state failed");
             qemu_mutex_unlock_iothread();
             goto out;
         }
diff --git a/migration/ram.c b/migration/ram.c
index 891f3b2..8f416d5 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2465,7 +2465,6 @@ static int ram_load(QEMUFile *f, void *opaque, int 
version_id)
      * be atomic
      */
     bool postcopy_running = postcopy_state_get() >= 
POSTCOPY_INCOMING_LISTENING;
-    bool need_flush = false;
 
     seq_iter++;
 
@@ -2500,7 +2499,6 @@ static int ram_load(QEMUFile *f, void *opaque, int 
version_id)
             /* After going into COLO, we should load the Page into colo_cache 
*/
             if (ram_cache_enable) {
                 host = colo_cache_from_block_offset(block, addr);
-                need_flush = true;
             } else {
                 host = host_from_ram_block_offset(block, addr);
             }
@@ -2594,9 +2592,6 @@ static int ram_load(QEMUFile *f, void *opaque, int 
version_id)
 
     rcu_read_unlock();
 
-    if (!ret  && ram_cache_enable && need_flush) {
-        colo_flush_ram_cache();
-    }
     DPRINTF("Completed load of VM with exit code %d seq iteration "
             "%" PRIu64 "\n", ret, seq_iter);
     return ret;
diff --git a/migration/savevm.c b/migration/savevm.c
index 60c7b57..1551fbb 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -50,6 +50,7 @@
 #include "qemu/iov.h"
 #include "block/snapshot.h"
 #include "block/qapi.h"
+#include "migration/colo.h"
 
 
 #ifndef ETH_P_RARP
@@ -923,6 +924,10 @@ void qemu_savevm_state_begin(QEMUFile *f,
             break;
         }
     }
+    if (migration_in_colo_state()) {
+        qemu_put_byte(f, QEMU_VM_EOF);
+        qemu_fflush(f);
+    }
 }
 
 /*
-- 
1.8.3.1