Mercurial > hg > release > icedtea7-forest-2.4 > hotspot
changeset 4094:f99a36499b8c
7192128: G1: Extend fix for 6948537 to G1's BOT
Summary: G1 does not appear to be immune to the issue described in CR 6948537 and increasing the size of old-generation PLABs appears to increase the liklihood of seeing the issue. Extend the fix for 6948537 to G1's BlockOffsetTable.
Reviewed-by: brutisso, jmasa
| author | johnc |
|---|---|
| date | Tue, 21 Aug 2012 10:05:57 -0700 |
| parents | 3958f0acde31 |
| children | 7383557659bd |
| files | src/cpu/sparc/vm/vm_version_sparc.cpp src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp |
| diffstat | 3 files changed, 32 insertions(+), 8 deletions(-) [+] |
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--- a/src/cpu/sparc/vm/vm_version_sparc.cpp Fri Aug 17 15:41:04 2012 -0700 +++ b/src/cpu/sparc/vm/vm_version_sparc.cpp Tue Aug 21 10:05:57 2012 -0700 @@ -106,10 +106,10 @@ if (FLAG_IS_DEFAULT(OptoLoopAlignment)) { FLAG_SET_DEFAULT(OptoLoopAlignment, 4); } - // When using CMS, we cannot use memset() in BOT updates because - // the sun4v/CMT version in libc_psr uses BIS which exposes - // "phantom zeros" to concurrent readers. See 6948537. - if (FLAG_IS_DEFAULT(UseMemSetInBOT) && UseConcMarkSweepGC) { + // When using CMS or G1, we cannot use memset() in BOT updates + // because the sun4v/CMT version in libc_psr uses BIS which + // exposes "phantom zeros" to concurrent readers. See 6948537. + if (FLAG_IS_DEFAULT(UseMemSetInBOT) && (UseConcMarkSweepGC || UseG1GC)) { FLAG_SET_DEFAULT(UseMemSetInBOT, false); } #ifdef _LP64
--- a/src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp Fri Aug 17 15:41:04 2012 -0700 +++ b/src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp Tue Aug 21 10:05:57 2012 -0700 @@ -1,5 +1,5 @@ /* - * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved. + * Copyright (c) 2001, 2012, 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 @@ -159,14 +159,30 @@ "right address out of range"); assert(left < right, "Heap addresses out of order"); size_t num_cards = pointer_delta(right, left) >> LogN_words; - memset(&_offset_array[index_for(left)], offset, num_cards); + if (UseMemSetInBOT) { + memset(&_offset_array[index_for(left)], offset, num_cards); + } else { + size_t i = index_for(left); + const size_t end = i + num_cards; + for (; i < end; i++) { + _offset_array[i] = offset; + } + } } void set_offset_array(size_t left, size_t right, u_char offset) { assert(right < _vs.committed_size(), "right address out of range"); - assert(left <= right, "indexes out of order"); + assert(left <= right, "indexes out of order"); size_t num_cards = right - left + 1; - memset(&_offset_array[left], offset, num_cards); + if (UseMemSetInBOT) { + memset(&_offset_array[left], offset, num_cards); + } else { + size_t i = left; + const size_t end = i + num_cards; + for (; i < end; i++) { + _offset_array[i] = offset; + } + } } void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const {
--- a/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp Fri Aug 17 15:41:04 2012 -0700 +++ b/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp Tue Aug 21 10:05:57 2012 -0700 @@ -1934,6 +1934,14 @@ clear_cset_start_regions(); guarantee(_task_queues != NULL, "task_queues allocation failure."); +#ifdef SPARC + // Issue a stern warning, but allow use for experimentation and debugging. + if (VM_Version::is_sun4v() && UseMemSetInBOT) { + assert(!FLAG_IS_DEFAULT(UseMemSetInBOT), "Error"); + warning("Experimental flag -XX:+UseMemSetInBOT is known to cause instability" + " on sun4v; please understand that you are using at your own risk!"); + } +#endif } jint G1CollectedHeap::initialize() {