Re: [PATCH 7/9] migration: Remember num of ramblocks to sync during recovery

[Fabiano Rosas]

Peter Xu  writes:

> Instead of only relying on the count of rp_sem, make the counter be part of
> RAMState so it can be used in both threads to synchronize on the process.
>
> rp_sem will be further reused as a way to kick the main thread, e.g., on
> recovery failures.
>
> Signed-off-by: Peter Xu 

Reviewed-by: Fabiano Rosas 

[PATCH 7/9] migration: Remember num of ramblocks to sync during recovery

[Peter Xu]

Instead of only relying on the count of rp_sem, make the counter be part of
RAMState so it can be used in both threads to synchronize on the process.

rp_sem will be further reused as a way to kick the main thread, e.g., on
recovery failures.

Signed-off-by: Peter Xu 
---
 migration/ram.c | 17 ++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/migration/ram.c b/migration/ram.c
index 814c59c17b..a9541c60b4 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -394,6 +394,14 @@ struct RAMState {
 /* Queue of outstanding page requests from the destination */
 QemuMutex src_page_req_mutex;
 QSIMPLEQ_HEAD(, RAMSrcPageRequest) src_page_requests;
+
+/*
+ * This is only used when postcopy is in recovery phase, to communicate
+ * between the migration thread and the return path thread on dirty
+ * bitmap synchronizations.  This field is unused in other stages of
+ * RAM migration.
+ */
+unsigned int postcopy_bmap_sync_requested;
 };
 typedef struct RAMState RAMState;
 
@@ -4135,20 +4143,20 @@ static int ram_dirty_bitmap_sync_all(MigrationState *s, 
RAMState *rs)
 {
 RAMBlock *block;
 QEMUFile *file = s->to_dst_file;
-int ramblock_count = 0;
 
 trace_ram_dirty_bitmap_sync_start();
 
+qatomic_set(>postcopy_bmap_sync_requested, 0);
 RAMBLOCK_FOREACH_NOT_IGNORED(block) {
 qemu_savevm_send_recv_bitmap(file, block->idstr);
 trace_ram_dirty_bitmap_request(block->idstr);
-ramblock_count++;
+qatomic_inc(>postcopy_bmap_sync_requested);
 }
 
 trace_ram_dirty_bitmap_sync_wait();
 
 /* Wait until all the ramblocks' dirty bitmap synced */
-while (ramblock_count--) {
+while (qatomic_read(>postcopy_bmap_sync_requested)) {
 qemu_sem_wait(>rp_state.rp_sem);
 }
 
@@ -4175,6 +4183,7 @@ int ram_dirty_bitmap_reload(MigrationState *s, RAMBlock 
*block, Error **errp)
 unsigned long *le_bitmap, nbits = block->used_length >> TARGET_PAGE_BITS;
 uint64_t local_size = DIV_ROUND_UP(nbits, 8);
 uint64_t size, end_mark;
+RAMState *rs = ram_state;
 
 trace_ram_dirty_bitmap_reload_begin(block->idstr);
 
@@ -4240,6 +4249,8 @@ int ram_dirty_bitmap_reload(MigrationState *s, RAMBlock 
*block, Error **errp)
 /* We'll recalculate migration_dirty_pages in ram_state_resume_prepare(). 
*/
 trace_ram_dirty_bitmap_reload_complete(block->idstr);
 
+qatomic_dec(>postcopy_bmap_sync_requested);
+
 /*
  * We succeeded to sync bitmap for current ramblock. If this is
  * the last one to sync, we need to notify the main send thread.
-- 
2.41.0