[Qemu-devel] [PATCH qemu v5 17/18] memory: Create FlatView directly

[Alexey Kardashevskiy <aik@ozlabs.ru>]

This avoids usual memory_region_transaction_commit() which rebuilds
all FVs.

On POWER8 with 255 CPUs, 255 virtio-net, 40 PCI bridges guest this brings
down the boot time from 25s to 20s and reduces the amount of temporary FVs
allocated during machine constructon (~800000 -> ~640000) and amount of
temporary dispatch trees (~370000 -> ~300000), the total memory footprint
goes down (18G -> 17G).

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
Changes:
v5:
* %s/flatview_update_topology_single/address_space_update_topology/g
* fixup after moving g_hash_table_replace() to generate_memory_topology()
---
 memory.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/memory.c b/memory.c
index 57e47e990f..5c21563745 100644
--- a/memory.c
+++ b/memory.c
@@ -1027,6 +1027,17 @@ static void address_space_set_flatview(AddressSpace *as)
     }
 }
 
+static void address_space_update_topology(AddressSpace *as)
+{
+    MemoryRegion *physmr = memory_region_get_flatview_root(as->root);
+
+    flatviews_init();
+    if (!g_hash_table_lookup(flat_views, physmr)) {
+        generate_memory_topology(physmr);
+    }
+    address_space_set_flatview(as);
+}
+
 void memory_region_transaction_begin(void)
 {
     qemu_flush_coalesced_mmio_buffer();
@@ -2738,7 +2749,6 @@ void memory_region_invalidate_mmio_ptr(MemoryRegion *mr, hwaddr offset,
 void address_space_init(AddressSpace *as, MemoryRegion *root, const char *name)
 {
     memory_region_ref(root);
-    memory_region_transaction_begin();
     as->root = root;
     as->current_map = NULL;
     as->ioeventfd_nb = 0;
@@ -2746,8 +2756,7 @@ void address_space_init(AddressSpace *as, MemoryRegion *root, const char *name)
     QTAILQ_INIT(&as->listeners);
     QTAILQ_INSERT_TAIL(&address_spaces, as, address_spaces_link);
     as->name = g_strdup(name ? name : "anonymous");
-    memory_region_update_pending |= root->enabled;
-    memory_region_transaction_commit();
+    address_space_update_topology(as);
 }
 
 static void do_address_space_destroy(AddressSpace *as)
-- 
2.11.0