@@ -48,6 +48,7 @@ static QTAILQ_HEAD(, AddressSpace) address_spaces
= QTAILQ_HEAD_INITIALIZER(address_spaces);
static GHashTable *flat_views;
+static FlatView *empty_view;
typedef struct AddrRange AddrRange;
@@ -746,22 +747,43 @@ static FlatView *generate_memory_topology(MemoryRegion *mr)
{
int i;
FlatView *view;
+ bool use_empty = false;
- view = flatview_new(mr);
+ if (!mr->enabled) {
+ use_empty = true;
+ } else {
+ view = flatview_new(mr);
+ if (mr) {
+ render_memory_region(view, mr, int128_zero(),
+ addrrange_make(int128_zero(), int128_2_64()),
+ false);
+ }
+ flatview_simplify(view);
- if (mr) {
- render_memory_region(view, mr, int128_zero(),
- addrrange_make(int128_zero(), int128_2_64()), false);
+ if (!view->nr) {
+ flatview_destroy(view);
+ use_empty = true;
+ }
}
- flatview_simplify(view);
- view->dispatch = address_space_dispatch_new(view);
- for (i = 0; i < view->nr; i++) {
- MemoryRegionSection mrs =
- section_from_flat_range(&view->ranges[i], view);
- flatview_add_to_dispatch(view, &mrs);
+ if (use_empty) {
+ if (!empty_view) {
+ empty_view = flatview_new(NULL);
+ }
+ view = empty_view;
+ flatview_ref(view);
}
- address_space_dispatch_compact(view->dispatch);
+
+ if (!view->dispatch) {
+ view->dispatch = address_space_dispatch_new(view);
+ for (i = 0; i < view->nr; i++) {
+ MemoryRegionSection mrs =
+ section_from_flat_range(&view->ranges[i], view);
+ flatview_add_to_dispatch(view, &mrs);
+ }
+ address_space_dispatch_compact(view->dispatch);
+ }
+
g_hash_table_replace(flat_views, mr, view);
return view;
This shares an cached empty FlatView among address spaces. The empty FV is used every time when a root MR renders into a FV without memory sections which happens when MR or its children are not enabled or zero-sized. The empty_view is not NULL to keep the rest of memory API intact; it also has a dispatch tree for the same reason. On POWER8 with 255 CPUs, 255 virtio-net, 40 PCI bridges guest this halves the amount of FlatView's in use (557 -> 260) and dispatch tables (~800000 -> ~370000), however the total memory footprint is pretty much the same as RCU is holding all these temporary FVs which are created (and then released) to make sure that they are empty and can be replaced with @empty_view. Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> --- Changes: v5: * generate_memory_topology() now destroys temporary FV directly as it is not in use anyway * check for mr->enabled and avoid even temporaty FV allocation --- memory.c | 44 +++++++++++++++++++++++++++++++++----------- 1 file changed, 33 insertions(+), 11 deletions(-)