[Qemu-devel] [RFC PATCH 35/36] block: allow customizing the granularity of the dirty bitmap

[Paolo Bonzini <pbonzini@redhat.com>]

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block-migration.c |    6 ++++--
 block.c           |   14 +++++++-------
 block.h           |    5 +----
 block/mirror.c    |   14 ++++----------
 4 files changed, 16 insertions(+), 23 deletions(-)

diff --git a/block-migration.c b/block-migration.c
index 6fdce1a..3b05c77 100644
--- a/block-migration.c
+++ b/block-migration.c
@@ -23,7 +23,8 @@
 #include "blockdev.h"
 #include <assert.h>
 
-#define BLOCK_SIZE (BDRV_SECTORS_PER_DIRTY_CHUNK << BDRV_SECTOR_BITS)
+#define BLOCK_SIZE                       (1 << 20)
+#define BDRV_SECTORS_PER_DIRTY_CHUNK     (BLOCK_SIZE >> BDRV_SECTOR_BITS)
 
 #define BLK_MIG_FLAG_DEVICE_BLOCK       0x01
 #define BLK_MIG_FLAG_EOS                0x02
@@ -264,7 +265,8 @@ static void set_dirty_tracking(int enable)
     BlkMigDevState *bmds;
 
     QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
-        bdrv_set_dirty_tracking(bmds->bs, enable);
+        bdrv_set_dirty_tracking(bmds->bs,
+                                enable ? BDRV_SECTORS_PER_DIRTY_CHUNK : 0);
     }
 }
 
diff --git a/block.c b/block.c
index b1d653f..e25b18a 100644
--- a/block.c
+++ b/block.c
@@ -4028,16 +4028,16 @@ void *qemu_blockalign(BlockDriverState *bs, size_t size)
     return qemu_memalign((bs && bs->buffer_alignment) ? bs->buffer_alignment : 512, size);
 }
 
-void bdrv_set_dirty_tracking(BlockDriverState *bs, int enable)
+void bdrv_set_dirty_tracking(BlockDriverState *bs, int granularity)
 {
     int64_t bitmap_size;
 
-    if (enable) {
-        if (!bs->dirty_bitmap) {
-            bitmap_size = (bdrv_getlength(bs) >> BDRV_SECTOR_BITS);
-            bs->dirty_bitmap = hbitmap_alloc(bitmap_size,
-                                             BDRV_LOG_SECTORS_PER_DIRTY_CHUNK);
-        }
+    assert((granularity & (granularity - 1)) == 0);
+
+    if (granularity) {
+        assert(!bs->dirty_bitmap);
+        bitmap_size = (bdrv_getlength(bs) >> BDRV_SECTOR_BITS);
+        bs->dirty_bitmap = hbitmap_alloc(bitmap_size, ffs(granularity) - 1);
     } else {
         if (bs->dirty_bitmap) {
             hbitmap_free(bs->dirty_bitmap);
diff --git a/block.h b/block.h
index a79f26b..546fc02 100644
--- a/block.h
+++ b/block.h
@@ -357,11 +357,8 @@ int bdrv_img_create(const char *filename, const char *fmt,
 void bdrv_set_buffer_alignment(BlockDriverState *bs, int align);
 void *qemu_blockalign(BlockDriverState *bs, size_t size);
 
-#define BDRV_SECTORS_PER_DIRTY_CHUNK     (1 << BDRV_LOG_SECTORS_PER_DIRTY_CHUNK)
-#define BDRV_LOG_SECTORS_PER_DIRTY_CHUNK 11
-
 struct HBitmapIter;
-void bdrv_set_dirty_tracking(BlockDriverState *bs, int enable);
+void bdrv_set_dirty_tracking(BlockDriverState *bs, int granularity);
 int bdrv_get_dirty(BlockDriverState *bs, int64_t sector);
 void bdrv_set_dirty(BlockDriverState *bs, int64_t cur_sector, int nr_sectors);
 void bdrv_reset_dirty(BlockDriverState *bs, int64_t cur_sector, int nr_sectors);
diff --git a/block/mirror.c b/block/mirror.c
index cc9f1fb..e09beaf 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -17,14 +17,8 @@
 #include "qemu/ratelimit.h"
 #include "bitmap.h"
 
-enum {
-    /*
-     * Size of data buffer for populating the image file.  This should be large
-     * enough to process multiple clusters in a single call, so that populating
-     * contiguous regions of the image is efficient.
-     */
-    BLOCK_SIZE = 512 * BDRV_SECTORS_PER_DIRTY_CHUNK, /* in bytes */
-};
+#define BLOCK_SIZE                       (1 << 20)
+#define BDRV_SECTORS_PER_DIRTY_CHUNK     (BLOCK_SIZE >> BDRV_SECTOR_BITS)
 
 #define SLICE_TIME 100000000ULL /* ns */
 
@@ -233,7 +227,7 @@ static void coroutine_fn mirror_run(void *opaque)
 immediate_exit:
     g_free(s->buf);
     g_free(s->cow_bitmap);
-    bdrv_set_dirty_tracking(bs, false);
+    bdrv_set_dirty_tracking(bs, 0);
     bdrv_iostatus_disable(s->target);
     if (s->synced && ret == 0) {
         ret = bdrv_flush(s->target);
@@ -344,7 +338,7 @@ void mirror_start(BlockDriverState *bs, BlockDriverState *target,
         }
     }
 
-    bdrv_set_dirty_tracking(bs, true);
+    bdrv_set_dirty_tracking(bs, BDRV_SECTORS_PER_DIRTY_CHUNK);
     bdrv_set_on_error(s->target, on_target_error, on_target_error);
     bdrv_iostatus_enable(s->target);
     s->common.co = qemu_coroutine_create(mirror_run);
-- 
1.7.10.2