[Qemu-devel] [PATCH 7/7] Maintaing number of dirty pages

[Juan Quintela]

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 <address@hidden>
---
 arch_init.c     |   15 +--------------
 cpu-all.h       |    1 +
 exec-obsolete.h |    8 ++++++++
 exec.c          |    2 ++
 4 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/arch_init.c b/arch_init.c
index 2aa77ff..77c3580 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -224,20 +224,7 @@ static uint64_t bytes_transferred;

 static ram_addr_t ram_save_remaining(void)
 {
-    RAMBlock *block;
-    ram_addr_t count = 0;
-
-    QLIST_FOREACH(block, &ram_list.blocks, next) {
-        ram_addr_t addr;
-        for (addr = 0; addr < block->length; addr += TARGET_PAGE_SIZE) {
-            if (memory_region_get_dirty(block->mr, addr, TARGET_PAGE_SIZE,
-                                        DIRTY_MEMORY_MIGRATION)) {
-                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 028528f..897210f 100644
--- a/cpu-all.h
+++ b/cpu-all.h
@@ -502,6 +502,7 @@ typedef struct RAMBlock {
 typedef struct RAMList {
     uint8_t *phys_dirty;
     QLIST_HEAD(, RAMBlock) blocks;
+    uint64_t dirty_pages;
 } RAMList;
 extern RAMList ram_list;

diff --git a/exec-obsolete.h b/exec-obsolete.h
index 792c831..2e54ac9 100644
--- a/exec-obsolete.h
+++ b/exec-obsolete.h
@@ -75,6 +75,10 @@ static inline int cpu_physical_memory_get_dirty(ram_addr_t 
start,

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

@@ -112,6 +116,10 @@ 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 (addr = start; addr < end; addr += TARGET_PAGE_SIZE) {
+        if (cpu_physical_memory_get_dirty(addr, TARGET_PAGE_SIZE,
+                                          MIGRATION_DIRTY_FLAG & dirty_flags)) 
{
+            ram_list.dirty_pages--;
+        }
         *p++ &= mask;
     }
 }
diff --git a/exec.c b/exec.c
index b6c7675..be4865c 100644
--- a/exec.c
+++ b/exec.c
@@ -2687,6 +2687,8 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void 
*host,
     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);

-- 
1.7.7.6