[Qemu-devel] [PATCH 14/22] exec: only check relevant bitmaps for cleanliness

[Paolo Bonzini]

Most of the time, not all bitmaps have to be marked as dirty;
do not do anything if the interesting ones are already dirty.
Previously, any clean bitmap would have cause all the bitmaps to be
marked dirty.

In fact, unless running TCG most of the time bitmap operations
are not done at all because memory_region_is_logging returns
zero.  In this case, skip cpu_physical_memory_range_includes_clean
as well.

With this patch, cpu_physical_memory_set_dirty_range is called
unconditionally, so there need not be anymore a separate call to
xen_modified_memory.

Signed-off-by: Paolo Bonzini <address@hidden>
---
 exec.c                  | 18 +++++++++---------
 include/exec/ram_addr.h | 19 +++++++++++++------
 2 files changed, 22 insertions(+), 15 deletions(-)

diff --git a/exec.c b/exec.c
index 94b7644..83c58ff 100644
--- a/exec.c
+++ b/exec.c
@@ -2236,16 +2236,16 @@ int cpu_memory_rw_debug(CPUState *cpu, target_ulong 
addr,
 static void invalidate_and_set_dirty(MemoryRegion *mr, hwaddr addr,
                                      hwaddr length)
 {
-    if (cpu_physical_memory_range_includes_clean(addr, length)) {
-        uint8_t dirty_log_mask = memory_region_is_logging(mr);
-        if (dirty_log_mask & (1 << DIRTY_MEMORY_CODE)) {
-            tb_invalidate_phys_range(addr, addr + length, 0);
-            dirty_log_mask &= ~(1 << DIRTY_MEMORY_CODE);
-        }
-        cpu_physical_memory_set_dirty_range(addr, length, dirty_log_mask);
-    } else {
-        xen_modified_memory(addr, length);
+    uint8_t dirty_log_mask = memory_region_is_logging(mr);
+    if (dirty_log_mask &&
+        !cpu_physical_memory_range_includes_clean(addr, length, 
dirty_log_mask)) {
+        dirty_log_mask = 0;
+    }
+    if (dirty_log_mask & (1 << DIRTY_MEMORY_CODE)) {
+        tb_invalidate_phys_range(addr, addr + length, 0);
+        dirty_log_mask &= ~(1 << DIRTY_MEMORY_CODE);
     }
+    cpu_physical_memory_set_dirty_range(addr, length, dirty_log_mask);
 }
 
 static int memory_access_size(MemoryRegion *mr, unsigned l, hwaddr addr)
diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
index 6c3b74e..b408408 100644
--- a/include/exec/ram_addr.h
+++ b/include/exec/ram_addr.h
@@ -90,13 +90,20 @@ static inline bool cpu_physical_memory_is_clean(ram_addr_t 
addr)
 }
 
 static inline bool cpu_physical_memory_range_includes_clean(ram_addr_t start,
-                                                            ram_addr_t length)
+                                                            ram_addr_t length,
+                                                            uint8_t mask)
 {
-    bool vga = cpu_physical_memory_get_clean(start, length, DIRTY_MEMORY_VGA);
-    bool code = cpu_physical_memory_get_clean(start, length, 
DIRTY_MEMORY_CODE);
-    bool migration =
-        cpu_physical_memory_get_clean(start, length, DIRTY_MEMORY_MIGRATION);
-    return vga || code || migration;
+    bool clean = false;
+    if (mask & (1 << DIRTY_MEMORY_VGA)) {
+        clean = cpu_physical_memory_get_clean(start, length, DIRTY_MEMORY_VGA);
+    }
+    if (!clean && (mask & (1 << DIRTY_MEMORY_CODE))) {
+        clean = cpu_physical_memory_get_clean(start, length, 
DIRTY_MEMORY_CODE);
+    }
+    if (!clean && (mask & (1 << DIRTY_MEMORY_MIGRATION))) {
+        clean = cpu_physical_memory_get_clean(start, length, 
DIRTY_MEMORY_MIGRATION);
+    }
+    return clean;
 }
 
 static inline void cpu_physical_memory_set_dirty_flag(ram_addr_t addr,
-- 
2.3.3