Mercurial > hg > graal-jvmci-8
diff src/share/vm/runtime/orderAccess.hpp @ 1711:a6bff45449bc
6973570: OrderAccess::storestore() scales poorly on multi-socket x64 and sparc: cache-line ping-ponging
Summary: volatile store to static variable removed in favour of a volatile store to stack to avoid excessive cache coherency traffic; verified that the volatile store is not elided by any of our current compilers.
Reviewed-by: dholmes, dice, jcoomes, kvn
author | ysr |
---|---|
date | Tue, 10 Aug 2010 14:53:35 -0700 |
parents | c18cbe5936b8 |
children | f95d63e2154a |
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--- a/src/share/vm/runtime/orderAccess.hpp Mon Aug 09 18:03:50 2010 -0700 +++ b/src/share/vm/runtime/orderAccess.hpp Tue Aug 10 14:53:35 2010 -0700 @@ -1,5 +1,5 @@ /* - * Copyright (c) 2003, 2009, Oracle and/or its affiliates. All rights reserved. + * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it @@ -166,6 +166,12 @@ // and release must include a sequence point, usually via a volatile memory // access. Other ways to guarantee a sequence point are, e.g., use of // indirect calls and linux's __asm__ volatile. +// Note: as of 6973570, we have replaced the originally static "dummy" field +// (see above) by a volatile store to the stack. All of the versions of the +// compilers that we currently use (SunStudio, gcc and VC++) respect the +// semantics of volatile here. If you build HotSpot using other +// compilers, you may need to verify that no compiler reordering occurs +// across the sequence point respresented by the volatile access. // // // os::is_MP Considered Redundant @@ -297,10 +303,6 @@ static void release_store_ptr_fence(volatile intptr_t* p, intptr_t v); static void release_store_ptr_fence(volatile void* p, void* v); - // In order to force a memory access, implementations may - // need a volatile externally visible dummy variable. - static volatile intptr_t dummy; - private: // This is a helper that invokes the StubRoutines::fence_entry() // routine if it exists, It should only be used by platforms that