[Qemu-devel] Re: [PATCH] qemu-kvm: Speed up of the dirty-bitmap-traveling

[OHMURA Kei <ohmura.kei@lab.ntt.co.jp>]

Thank you for your comments.  We have implemented the code which applied your 
comments.  This is patch for qemu-kvm.c.

Signed-off-by: OHMURA Kei <ohmura.kei@lab.ntt.co.jp>
---
 qemu-kvm.c |   31 +++++++++++++++++++------------
 1 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/qemu-kvm.c b/qemu-kvm.c
index a305907..d7474ea 100644
--- a/qemu-kvm.c
+++ b/qemu-kvm.c
@@ -2438,27 +2438,34 @@ static int kvm_get_dirty_pages_log_range(unsigned long start_addr,
                                          unsigned long offset,
                                          unsigned long mem_size)
 {
-    unsigned int i, j, n = 0;
+    unsigned int i, j, k, start, end;
     unsigned char c;
     unsigned long page_number, addr, addr1;
     ram_addr_t ram_addr;
-    unsigned int len = ((mem_size / TARGET_PAGE_SIZE) + 7) / 8;
+    unsigned int len = ((mem_size / TARGET_PAGE_SIZE) + TARGET_LONG_BITS - 1) /
+        TARGET_LONG_BITS;
+    unsigned long *bitmap_ul = (unsigned long *)bitmap;
 
     /* 
      * bitmap-traveling is faster than memory-traveling (for addr...) 
      * especially when most of the memory is not dirty.
      */
     for (i = 0; i < len; i++) {
-        c = bitmap[i];
-        while (c > 0) {
-            j = ffsl(c) - 1;
-            c &= ~(1u << j);
-            page_number = i * 8 + j;
-            addr1 = page_number * TARGET_PAGE_SIZE;
-            addr = offset + addr1;
-            ram_addr = cpu_get_physical_page_desc(addr);
-            cpu_physical_memory_set_dirty(ram_addr);
-            n++;
+        if (bitmap_ul[i] != 0) {
+            start = i * TARGET_LONG_SIZE;
+            end = (i + 1) * TARGET_LONG_SIZE;
+            for (j = start; j < end; j++) {
+                c = bitmap[j];
+                while (c > 0) {
+                    k = ffsl(c) - 1;
+                    c &= ~(1u << k);
+                    page_number = j * 8 + k;
+                    addr1 = page_number * TARGET_PAGE_SIZE;
+                    addr = offset + addr1;
+                    ram_addr = cpu_get_physical_page_desc(addr);
+                    cpu_physical_memory_set_dirty(ram_addr);
+                }
+            }
         }
     }
     return 0;
-- 
1.6.3.3