[PULL 02/17] migration/ram: Reduce unnecessary rate limiting

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: Kunkun Jiang <jiangkunkun@huawei.com>

When the host page is a huge page and something is sent in the
current iteration, migration_rate_limit() should be executed.
If not, it can be omitted.

Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
Reviewed-by: David Edmondson <david.edmondson@oracle.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20210316125716.1243-2-jiangkunkun@huawei.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 migration/ram.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/migration/ram.c b/migration/ram.c
index bee2756cd3..00b579b981 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2035,8 +2035,13 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss,
 
         pages += tmppages;
         pss->page++;
-        /* Allow rate limiting to happen in the middle of huge pages */
-        migration_rate_limit();
+        /*
+         * Allow rate limiting to happen in the middle of huge pages if
+         * something is sent in the current iteration.
+         */
+        if (pagesize_bits > 1 && tmppages > 0) {
+            migration_rate_limit();
+        }
     } while ((pss->page & (pagesize_bits - 1)) &&
              offset_in_ramblock(pss->block,
                                 ((ram_addr_t)pss->page) << TARGET_PAGE_BITS));
-- 
2.31.1