block-migration: limit the memory usage

If we set migration speed in a very large value, block-migration will try to read
all data to the memory. Because
    (block_mig_state.submitted + block_mig_state.read_done) * BLOCK_SIZE
will be overflow, and it will be always less than rate limit.

There is no need to read too many data into memory when the rate limit is very large.
So limit the memory usage can fix the overflow problem.

Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

diff --git a/migration/block.c b/migration/block.c
index 310e2b36dc9a1b28591abea876331218209bf808..656f38f341dadd410501535995b646656fe8bc95 100644 (file)
--- a/migration/block.c
+++ b/migration/block.c
@@ -36,6 +36,8 @@
 
 #define MAX_IS_ALLOCATED_SEARCH 65536
 
+#define MAX_INFLIGHT_IO 512
+
 //#define DEBUG_BLK_MIGRATION
 
 #ifdef DEBUG_BLK_MIGRATION
@@ -665,7 +667,10 @@ static int block_save_iterate(QEMUFile *f, void *opaque)
     blk_mig_lock();
     while ((block_mig_state.submitted +
             block_mig_state.read_done) * BLOCK_SIZE <
-           qemu_file_get_rate_limit(f)) {
+           qemu_file_get_rate_limit(f) &&
+           (block_mig_state.submitted +
+            block_mig_state.read_done) <
+           MAX_INFLIGHT_IO) {
         blk_mig_unlock();
         if (block_mig_state.bulk_completed == 0) {
             /* first finish the bulk phase */