[Qemu-devel] [PATCH 10/10] Maintaing number of dirty pages

[Juan Quintela]

From: Juan Quintela <quint...@trasno.org>

Calculate the number of dirty pages takes a lot on hosts with lots
of memory.  Just maintain how many pages are dirty.  Only sync bitmaps
if number is small enough.

Signed-off-by: Juan Quintela <quint...@trasno.org>
Signed-off-by: Juan Quintela <quint...@redhat.com>
---
 arch_init.c |   15 +--------------
 cpu-all.h   |    7 +++++++
 exec.c      |    1 +
 3 files changed, 9 insertions(+), 14 deletions(-)

diff --git a/arch_init.c b/arch_init.c
index b463798..c2bc144 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -176,20 +176,7 @@ static uint64_t bytes_transferred;

 static uint64_t ram_save_remaining(void)
 {
-    RAMBlock *block;
-    uint64_t count = 0;
-
-    QLIST_FOREACH(block, &ram_list.blocks, next) {
-        ram_addr_t addr;
-        for (addr = block->offset; addr < block->offset + block->length;
-             addr += TARGET_PAGE_SIZE) {
-            if (cpu_physical_memory_get_dirty(addr, MIGRATION_DIRTY_FLAG)) {
-                count++;
-            }
-        }
-    }
-
-    return count;
+    return ram_list.dirty_pages;
 }

 uint64_t ram_bytes_remaining(void)
diff --git a/cpu-all.h b/cpu-all.h
index 30ae17d..5dc27c6 100644
--- a/cpu-all.h
+++ b/cpu-all.h
@@ -874,6 +874,7 @@ typedef struct RAMBlock {

 typedef struct RAMList {
     uint8_t *phys_dirty;
+    uint64_t dirty_pages;
     QLIST_HEAD(ram, RAMBlock) blocks;
 } RAMList;
 extern RAMList ram_list;
@@ -922,6 +923,9 @@ static inline int cpu_physical_memory_get_dirty(ram_addr_t 
addr,

 static inline void cpu_physical_memory_set_dirty(ram_addr_t addr)
 {
+    if (!cpu_physical_memory_get_dirty(addr, MIGRATION_DIRTY_FLAG))
+        ram_list.dirty_pages++;
+
     ram_list.phys_dirty[addr >> TARGET_PAGE_BITS] = 0xff;
 }

@@ -942,6 +946,9 @@ static inline void 
cpu_physical_memory_mask_dirty_range(ram_addr_t start,
     mask = ~dirty_flags;
     p = ram_list.phys_dirty + (start >> TARGET_PAGE_BITS);
     for (i = 0; i < len; i++) {
+        if (cpu_physical_memory_get_dirty(start + i * TARGET_PAGE_SIZE,
+                                          MIGRATION_DIRTY_FLAG & dirty_flags))
+            ram_list.dirty_pages--;
         p[i] &= mask;
     }
 }
diff --git a/exec.c b/exec.c
index f5b2386..ca2506e 100644
--- a/exec.c
+++ b/exec.c
@@ -2866,6 +2866,7 @@ ram_addr_t qemu_ram_alloc_from_ptr(DeviceState *dev, 
const char *name,
                                        last_ram_offset() >> TARGET_PAGE_BITS);
     memset(ram_list.phys_dirty + (new_block->offset >> TARGET_PAGE_BITS),
            0xff, size >> TARGET_PAGE_BITS);
+    ram_list.dirty_pages += size >> TARGET_PAGE_BITS;

     if (kvm_enabled())
         kvm_setup_guest_memory(new_block->host, size);
-- 
1.7.3.2