[PATCH v4 08/12] migration/dirtyrate: skip sampling ramblock with size below MIN_RAMBLOCK_SIZE

[Chuan Zheng]

In order to sample real RAM, skip ramblock with size below MIN_RAMBLOCK_SIZE
which is set as 128M.

Signed-off-by: Chuan Zheng <zhengchuan@huawei.com>
---
 migration/dirtyrate.c | 24 ++++++++++++++++++++++++
 migration/dirtyrate.h | 10 ++++++++++
 2 files changed, 34 insertions(+)

diff --git a/migration/dirtyrate.c b/migration/dirtyrate.c
index 050270d..bd398b7 100644
--- a/migration/dirtyrate.c
+++ b/migration/dirtyrate.c
@@ -173,6 +173,24 @@ alloc_ramblock_dirty_info(int *block_index,
     return block_dinfo;
 }
 
+static int skip_sample_ramblock(RAMBlock *block)
+{
+    int64_t ramblock_size;
+
+    /* ramblock size in MB */
+    ramblock_size = qemu_ram_get_used_length(block) >> DIRTYRATE_PAGE_SHIFT_MB;
+
+    /*
+     * Consider ramblock with size larger than 128M is what we
+     * want to sample.
+     */
+    if (ramblock_size < MIN_RAMBLOCK_SIZE) {
+        return -1;
+    }
+
+    return 0;
+}
+
 static int record_ramblock_hash_info(struct RamblockDirtyInfo **block_dinfo,
                                      struct DirtyRateConfig config,
                                      int *block_index)
@@ -183,6 +201,9 @@ static int record_ramblock_hash_info(struct 
RamblockDirtyInfo **block_dinfo,
     int index = 0;
 
     RAMBLOCK_FOREACH_MIGRATABLE(block) {
+        if (skip_sample_ramblock(block) < 0) {
+            continue;
+        }
         dinfo = alloc_ramblock_dirty_info(&index, dinfo);
         if (dinfo == NULL) {
             return -1;
@@ -249,6 +270,9 @@ static int compare_page_hash_info(struct RamblockDirtyInfo 
*info,
     RAMBlock *block = NULL;
 
     RAMBLOCK_FOREACH_MIGRATABLE(block) {
+        if (skip_sample_ramblock(block) < 0) {
+            continue;
+        }
         block_dinfo = NULL;
         if (!find_page_matched(block, info, block_index + 1, &block_dinfo)) {
             continue;
diff --git a/migration/dirtyrate.h b/migration/dirtyrate.h
index 5050add..41bc264 100644
--- a/migration/dirtyrate.h
+++ b/migration/dirtyrate.h
@@ -35,10 +35,20 @@
 #define DIRTYRATE_PAGE_SHIFT_KB                   12
 
 /*
+ * Sample page size MB shift
+ */
+#define DIRTYRATE_PAGE_SHIFT_MB                   20
+
+/*
  * Sample page size 1G shift
  */
 #define DIRTYRATE_PAGE_SHIFT_GB                   30
 
+/*
+ * minimum ramblock size to sampled
+ */
+#define MIN_RAMBLOCK_SIZE                         128
+
 /* Take 1s as default for calculation duration */
 #define DEFAULT_FETCH_DIRTYRATE_TIME_SEC          1
 
-- 
1.8.3.1