[Qemu-devel] [RFC v3 03/56] memory: merge adjacent segments of a single memory region

[Avi Kivity <avi@redhat.com>]

Simple implementations of memory routers, for example the Cirrus VGA memory banks
or the 440FX PAM registers can generate adjacent memory regions which are contiguous.
Detect these and merge them; this saves kvm memory slots and shortens lookup times.

Signed-off-by: Avi Kivity <avi@redhat.com>
---
 memory.c |   22 ++++++++++++++++++++++
 1 files changed, 22 insertions(+), 0 deletions(-)

diff --git a/memory.c b/memory.c
index a569666..339bea3 100644
--- a/memory.c
+++ b/memory.c
@@ -122,6 +122,27 @@ static void flatview_destroy(FlatView *view)
     qemu_free(view->ranges);
 }
 
+/* Attempt to simplify a view by merging ajacent ranges */
+static void flatview_simplify(FlatView *view)
+{
+    unsigned i;
+    FlatRange *r1, *r2;
+
+    for (i = 0; i + 1 < view->nr; ++i) {
+        r1 = &view->ranges[i];
+        r2 = &view->ranges[i+1];
+        if (addrrange_end(r1->addr) == r2->addr.start
+            && r1->mr == r2->mr
+            && r1->offset_in_region + r1->addr.size == r2->offset_in_region
+            && r1->dirty_log_mask == r2->dirty_log_mask) {
+            r1->addr.size += r2->addr.size;
+            memmove(r2, r2 + 1, (view->nr - (i + 2)) * sizeof(*r2));
+            --view->nr;
+            --i;
+        }
+    }
+}
+
 /* Render a memory region into the global view.  Ranges in @view obscure
  * ranges in @mr.
  */
@@ -209,6 +230,7 @@ static FlatView generate_memory_topology(MemoryRegion *mr)
     flatview_init(&view);
 
     render_memory_region(&view, mr, 0, addrrange_make(0, UINT64_MAX));
+    flatview_simplify(&view);
 
     return view;
 }
-- 
1.7.5.3