Add MAP_FIXED to Uncommit calls to see if that has an effect on GMail...

src/platform-freebsd.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 316 matching lines @@
     return false;
   }
 
   UpdateAllocatedSpaceLimits(address, size);
   return true;
 }
 
 
 bool VirtualMemory::Uncommit(void* address, size_t size) {
   return mmap(address, size, PROT_NONE,
-              MAP_PRIVATE | MAP_ANON | MAP_NORESERVE,
+              MAP_PRIVATE | MAP_ANON | MAP_NORESERVE | MAP_FIXED,
               kMmapFd, kMmapFdOffset) != MAP_FAILED;
 }
 
 
 class ThreadHandle::PlatformData : public Malloced {
  public:
   explicit PlatformData(ThreadHandle::Kind kind) {
     Initialize(kind);
   }
 
@@ skipping 282 matching lines @@
   }
 
   // This sampler is no longer the active sampler.
   active_sampler_ = NULL;
   active_ = false;
 }
 
 #endif  // ENABLE_LOGGING_AND_PROFILING
 
 } }  // namespace v8::internal