commit 374f2981d1f10bc4307f250f24b2a7ddb9b14be0
author Paolo Bonzini <pbonzini@redhat.com> Fri May 17 12:37:03 2013 +0200
committer Paolo Bonzini <pbonzini@redhat.com> Mon Feb 02 16:55:10 2015 +0100
tree b8a960af49a9c5c84ee4ce2efa1b64363cf1d529
parent b476c99d01519277e3494a10dc0329d07157ae02

memory: protect current_map by RCU

Replace the flat_view_mutex with RCU, avoiding futex contention for
dataplane on large systems and many iothreads.

Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/exec/memory.h

diff --git a/include/exec/memory.h b/include/exec/memory.h
index 0cd96b1..06ffa1d 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -33,6 +33,7 @@
 #include "qemu/notify.h"
 #include "qapi/error.h"
 #include "qom/object.h"
+#include "qemu/rcu.h"
 
 #define MAX_PHYS_ADDR_SPACE_BITS 62
 #define MAX_PHYS_ADDR            (((hwaddr)1 << MAX_PHYS_ADDR_SPACE_BITS) - 1)
@@ -207,9 +208,13 @@
  */
 struct AddressSpace {
     /* All fields are private. */
+    struct rcu_head rcu;
     char *name;
     MemoryRegion *root;
+
+    /* Accessed via RCU.  */
     struct FlatView *current_map;
+
     int ioeventfd_nb;
     struct MemoryRegionIoeventfd *ioeventfds;
     struct AddressSpaceDispatch *dispatch;