Re: [Qemu-devel] [PATCH v6 07/10] qmp: Add support of "dirty-bitmap" sync mode for drive-backup

[Vladimir Sementsov-Ogievskiy]

@@ -317,7 +321,21 @@ static void coroutine_fn backup_run(void *opaque)
                 if (alloced == 0) {
                     continue;
                 }
+            } else if (job->sync_mode == MIRROR_SYNC_MODE_DIRTY_BITMAP) {
+                int i, dirty = 0;
+                for (i = 0; i < BACKUP_SECTORS_PER_CLUSTER;
+                     i += job->sync_bitmap_gran) {
+                    if (bdrv_get_dirty(bs, job->sync_bitmap,
+                            start * BACKUP_SECTORS_PER_CLUSTER + i)) {
+                        dirty = 1;
+                        break;
+                    }
+                }
+                if (!dirty) {
+                    continue;
+                }
             }
+

With such solution we don't use the power of HBitmap, which provides "hbitmap_iter_skip_words", with O(log(n)) complexity. Here we look through the whole bitmap (O(n)), instead of jumping to the next dirty bit.

-- 
С уважением,
Владимир