[Qemu-devel] [PATCH] block/mirror: Sleep periodically during bitmap scanning

[Fam Zheng <famz@redhat.com>]

Before, we only yield after initializing dirty bitmap, where the QMP
command would return. That may take very long, and guest IO will be
blocked.

Add sleep points like the later mirror iterations.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 block/mirror.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/block/mirror.c b/block/mirror.c
index 1a1d997..baed225 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -467,11 +467,23 @@ static void coroutine_fn mirror_run(void *opaque)
     sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
     mirror_free_init(s);
 
+    last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
     if (!s->is_none_mode) {
         /* First part, loop on the sectors and initialize the dirty bitmap.  */
         BlockDriverState *base = s->base;
         for (sector_num = 0; sector_num < end; ) {
             int64_t next = (sector_num | (sectors_per_chunk - 1)) + 1;
+            int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
+
+            if (now - last_pause_ns > SLICE_TIME) {
+                last_pause_ns = now;
+                block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, 0);
+            }
+
+            if (block_job_is_cancelled(&s->common)) {
+                goto immediate_exit;
+            }
+
             ret = bdrv_is_allocated_above(bs, base,
                                           sector_num, next - sector_num, &n);
 
@@ -490,7 +502,6 @@ static void coroutine_fn mirror_run(void *opaque)
     }
 
     bdrv_dirty_iter_init(s->dirty_bitmap, &s->hbi);
-    last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
     for (;;) {
         uint64_t delay_ns = 0;
         int64_t cnt;
-- 
2.4.0