[Qemu-devel] [PATCH v2 2/3] memory: optimize qemu_get_ram_ptr and qemu_ram_ptr_length

[Gonglei]

these two functions consume too much cpu overhead to
find the RAMBlock by ram address.

After this patch, we can pass the RAMBlock pointer
to them so that they don't need to find the RAMBlock
anymore most of the time. We can get better performance
in address translation processing.

Signed-off-by: Gonglei <address@hidden>
---
 exec.c                | 46 ++++++++++++++++++++++++++++------------------
 include/exec/memory.h |  4 ++--
 memory.c              |  2 +-
 3 files changed, 31 insertions(+), 21 deletions(-)

diff --git a/exec.c b/exec.c
index 4c0114a..c62c439 100644
--- a/exec.c
+++ b/exec.c
@@ -1868,9 +1868,13 @@ void *qemu_get_ram_block_host_ptr(ram_addr_t addr)
  *
  * Called within RCU critical section.
  */
-void *qemu_get_ram_ptr(ram_addr_t addr)
+void *qemu_get_ram_ptr(RAMBlock *ram_block, ram_addr_t addr)
 {
-    RAMBlock *block = qemu_get_ram_block(addr);
+    RAMBlock *block = ram_block;
+
+    if (block == NULL) {
+        block = qemu_get_ram_block(addr);
+    }
 
     if (xen_enabled() && block->host == NULL) {
         /* We need to check if the requested address is in the RAM
@@ -1891,15 +1895,18 @@ void *qemu_get_ram_ptr(ram_addr_t addr)
  *
  * Called within RCU critical section.
  */
-static void *qemu_ram_ptr_length(ram_addr_t addr, hwaddr *size)
+static void *qemu_ram_ptr_length(RAMBlock *ram_block, ram_addr_t addr,
+                                 hwaddr *size)
 {
-    RAMBlock *block;
+    RAMBlock *block = ram_block;
     ram_addr_t offset_inside_block;
     if (*size == 0) {
         return NULL;
     }
 
-    block = qemu_get_ram_block(addr);
+    if (block == NULL) {
+        block = qemu_get_ram_block(addr);
+    }
     offset_inside_block = addr - block->offset;
     *size = MIN(*size, block->max_length - offset_inside_block);
 
@@ -2027,13 +2034,13 @@ static void notdirty_mem_write(void *opaque, hwaddr 
ram_addr,
     }
     switch (size) {
     case 1:
-        stb_p(qemu_get_ram_ptr(ram_addr), val);
+        stb_p(qemu_get_ram_ptr(NULL, ram_addr), val);
         break;
     case 2:
-        stw_p(qemu_get_ram_ptr(ram_addr), val);
+        stw_p(qemu_get_ram_ptr(NULL, ram_addr), val);
         break;
     case 4:
-        stl_p(qemu_get_ram_ptr(ram_addr), val);
+        stl_p(qemu_get_ram_ptr(NULL, ram_addr), val);
         break;
     default:
         abort();
@@ -2609,7 +2616,7 @@ static MemTxResult 
address_space_write_continue(AddressSpace *as, hwaddr addr,
         } else {
             addr1 += memory_region_get_ram_addr(mr);
             /* RAM case */
-            ptr = qemu_get_ram_ptr(addr1);
+            ptr = qemu_get_ram_ptr(mr->ram_block, addr1);
             memcpy(ptr, buf, l);
             invalidate_and_set_dirty(mr, addr1, l);
         }
@@ -2700,7 +2707,7 @@ MemTxResult address_space_read_continue(AddressSpace *as, 
hwaddr addr,
             }
         } else {
             /* RAM case */
-            ptr = qemu_get_ram_ptr(mr->ram_addr + addr1);
+            ptr = qemu_get_ram_ptr(mr->ram_block, mr->ram_addr + addr1);
             memcpy(buf, ptr, l);
         }
 
@@ -2785,7 +2792,7 @@ static inline void 
cpu_physical_memory_write_rom_internal(AddressSpace *as,
         } else {
             addr1 += memory_region_get_ram_addr(mr);
             /* ROM/RAM case */
-            ptr = qemu_get_ram_ptr(addr1);
+            ptr = qemu_get_ram_ptr(mr->ram_block, addr1);
             switch (type) {
             case WRITE_DATA:
                 memcpy(ptr, buf, l);
@@ -2997,7 +3004,7 @@ void *address_space_map(AddressSpace *as,
 
     memory_region_ref(mr);
     *plen = done;
-    ptr = qemu_ram_ptr_length(raddr + base, plen);
+    ptr = qemu_ram_ptr_length(mr->ram_block, raddr + base, plen);
     rcu_read_unlock();
 
     return ptr;
@@ -3081,7 +3088,8 @@ static inline uint32_t 
address_space_ldl_internal(AddressSpace *as, hwaddr addr,
 #endif
     } else {
         /* RAM case */
-        ptr = qemu_get_ram_ptr((memory_region_get_ram_addr(mr)
+        ptr = qemu_get_ram_ptr(mr->ram_block,
+                               (memory_region_get_ram_addr(mr)
                                 & TARGET_PAGE_MASK)
                                + addr1);
         switch (endian) {
@@ -3176,7 +3184,8 @@ static inline uint64_t 
address_space_ldq_internal(AddressSpace *as, hwaddr addr,
 #endif
     } else {
         /* RAM case */
-        ptr = qemu_get_ram_ptr((memory_region_get_ram_addr(mr)
+        ptr = qemu_get_ram_ptr(mr->ram_block,
+                               (memory_region_get_ram_addr(mr)
                                 & TARGET_PAGE_MASK)
                                + addr1);
         switch (endian) {
@@ -3291,7 +3300,8 @@ static inline uint32_t 
address_space_lduw_internal(AddressSpace *as,
 #endif
     } else {
         /* RAM case */
-        ptr = qemu_get_ram_ptr((memory_region_get_ram_addr(mr)
+        ptr = qemu_get_ram_ptr(mr->ram_block,
+                               (memory_region_get_ram_addr(mr)
                                 & TARGET_PAGE_MASK)
                                + addr1);
         switch (endian) {
@@ -3376,7 +3386,7 @@ void address_space_stl_notdirty(AddressSpace *as, hwaddr 
addr, uint32_t val,
         r = memory_region_dispatch_write(mr, addr1, val, 4, attrs);
     } else {
         addr1 += memory_region_get_ram_addr(mr) & TARGET_PAGE_MASK;
-        ptr = qemu_get_ram_ptr(addr1);
+        ptr = qemu_get_ram_ptr(mr->ram_block, addr1);
         stl_p(ptr, val);
 
         dirty_log_mask = memory_region_get_dirty_log_mask(mr);
@@ -3431,7 +3441,7 @@ static inline void 
address_space_stl_internal(AddressSpace *as,
     } else {
         /* RAM case */
         addr1 += memory_region_get_ram_addr(mr) & TARGET_PAGE_MASK;
-        ptr = qemu_get_ram_ptr(addr1);
+        ptr = qemu_get_ram_ptr(mr->ram_block, addr1);
         switch (endian) {
         case DEVICE_LITTLE_ENDIAN:
             stl_le_p(ptr, val);
@@ -3541,7 +3551,7 @@ static inline void 
address_space_stw_internal(AddressSpace *as,
     } else {
         /* RAM case */
         addr1 += memory_region_get_ram_addr(mr) & TARGET_PAGE_MASK;
-        ptr = qemu_get_ram_ptr(addr1);
+        ptr = qemu_get_ram_ptr(mr->ram_block, addr1);
         switch (endian) {
         case DEVICE_LITTLE_ENDIAN:
             stw_le_p(ptr, val);
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 4025729..1cf2e51 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -1391,7 +1391,7 @@ MemTxResult address_space_read_continue(AddressSpace *as, 
hwaddr addr,
                                        MemoryRegion *mr);
 MemTxResult address_space_read_full(AddressSpace *as, hwaddr addr,
                                     MemTxAttrs attrs, uint8_t *buf, int len);
-void *qemu_get_ram_ptr(ram_addr_t addr);
+void *qemu_get_ram_ptr(RAMBlock *ram_block, ram_addr_t addr);
 
 static inline bool memory_access_is_direct(MemoryRegion *mr, bool is_write)
 {
@@ -1432,7 +1432,7 @@ MemTxResult address_space_read(AddressSpace *as, hwaddr 
addr, MemTxAttrs attrs,
             mr = address_space_translate(as, addr, &addr1, &l, false);
             if (len == l && memory_access_is_direct(mr, false)) {
                 addr1 += memory_region_get_ram_addr(mr);
-                ptr = qemu_get_ram_ptr(addr1);
+                ptr = qemu_get_ram_ptr(mr->ram_block, addr1);
                 memcpy(buf, ptr, len);
             } else {
                 result = address_space_read_continue(as, addr, attrs, buf, len,
diff --git a/memory.c b/memory.c
index b4451dd..0dd9695 100644
--- a/memory.c
+++ b/memory.c
@@ -1570,7 +1570,7 @@ void *memory_region_get_ram_ptr(MemoryRegion *mr)
         mr = mr->alias;
     }
     assert(mr->ram_addr != RAM_ADDR_INVALID);
-    ptr = qemu_get_ram_ptr(mr->ram_addr & TARGET_PAGE_MASK);
+    ptr = qemu_get_ram_ptr(mr->ram_block, mr->ram_addr & TARGET_PAGE_MASK);
     rcu_read_unlock();
 
     return ptr + offset;
-- 
1.8.5.2