On 03/14/2018 10:51 AM, Michael S. Tsirkin wrote:
On Wed, Mar 14, 2018 at 10:41:36AM +0800, Wei Wang wrote:
On 03/14/2018 12:35 AM, Michael S. Tsirkin wrote:
On Wed, Mar 07, 2018 at 08:34:25PM +0800, Wei Wang wrote:
Start the free page optimization after the migration bitmap is
synchronized. This can't be used in the stop&copy phase since the guest
is paused. Make sure the guest reporting has stopped before
synchronizing the migration dirty bitmap. Currently, the optimization is
added to precopy only.

Signed-off-by: Wei Wang <wei.w.w...@intel.com>
CC: Dr. David Alan Gilbert <dgilb...@redhat.com>
CC: Juan Quintela <quint...@redhat.com>
CC: Michael S. Tsirkin <m...@redhat.com>
   migration/ram.c | 19 ++++++++++++++++++-
   1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/migration/ram.c b/migration/ram.c
index e172798..7b4c9b1 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -51,6 +51,8 @@
   #include "qemu/rcu_queue.h"
   #include "migration/colo.h"
   #include "migration/block.h"
+#include "sysemu/balloon.h"
+#include "sysemu/sysemu.h"
   /* ram save/restore */
@@ -208,6 +210,8 @@ struct RAMState {
       uint32_t last_version;
       /* We are in the first round */
       bool ram_bulk_stage;
+    /* The free pages optimization feature is supported */
+    bool free_page_support;
       /* How many times we have dirty too many pages */
       int dirty_rate_high_cnt;
       /* these variables are used for bitmap sync */
@@ -775,7 +779,7 @@ unsigned long migration_bitmap_find_dirty(RAMState *rs, 
RAMBlock *rb,
       unsigned long *bitmap = rb->bmap;
       unsigned long next;
-    if (rs->ram_bulk_stage && start > 0) {
+    if (rs->ram_bulk_stage && start > 0 && !rs->free_page_support) {
           next = start + 1;
       } else {
           next = find_next_bit(bitmap, size, start);
@@ -833,6 +837,10 @@ static void migration_bitmap_sync(RAMState *rs)
       int64_t end_time;
       uint64_t bytes_xfer_now;
+    if (rs->free_page_support) {
+        balloon_free_page_stop();
+    }
       if (!rs->time_last_bitmap_sync) {
@@ -899,6 +907,10 @@ static void migration_bitmap_sync(RAMState *rs)
       if (migrate_use_events()) {
           qapi_event_send_migration_pass(ram_counters.dirty_sync_count, NULL);
+    if (rs->free_page_support && runstate_is_running()) {
+        balloon_free_page_start();
+    }
I think some of these conditions should go into

Checking runstate is generally problematic unless you
also handle run state change notifiers as it can
be manipulated from QMP.
How about moving the check of runstate to

while (dev->free_page_report_status < FREE_PAGE_REPORT_S_STOP &&
runstate_is_running()) {
Hard to tell on the outset. E.g. why is just stop affected?  Pls add
comments explaining what happens if VM is not running when start or stop
is called.

In this case, I think we won't need a notifier - if the run state is changed
by qmp, the optimization thread will just exist.
But you need to wake it up and notify the guest presumably?

I think it's not necessary to wake it up, because when the VM is not running, there will be no hints reported to the vq, and the optimization thread exits. (there is no issue in that case) Probably we can add a notifier which calls virtio_balloon_free_page_stop() when qmp wakes up the VM.


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