Mercurial > hg > truffle
comparison src/share/vm/memory/genCollectedHeap.hpp @ 1027:39b01ab7035a
6888898: CMS: ReduceInitialCardMarks unsafe in the presence of cms precleaning
6889757: G1: enable card mark elision for initializing writes from compiled code (ReduceInitialCardMarks)
Summary: Defer the (compiler-elided) card-mark upon a slow-path allocation until after the store and before the next subsequent safepoint; G1 now answers yes to can_elide_tlab_write_barriers().
Reviewed-by: jcoomes, kvn, never
| author | ysr |
|---|---|
| date | Fri, 16 Oct 2009 02:05:46 -0700 |
| parents | 148e5441d916 |
| children | 052a899eec3e |
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| 1025:1ee412f7fec9 | 1027:39b01ab7035a |
|---|---|
| 256 // Can a compiler initialize a new object without store barriers? | 256 // Can a compiler initialize a new object without store barriers? |
| 257 // This permission only extends from the creation of a new object | 257 // This permission only extends from the creation of a new object |
| 258 // via a TLAB up to the first subsequent safepoint. | 258 // via a TLAB up to the first subsequent safepoint. |
| 259 virtual bool can_elide_tlab_store_barriers() const { | 259 virtual bool can_elide_tlab_store_barriers() const { |
| 260 return true; | 260 return true; |
| 261 } | |
| 262 | |
| 263 // We don't need barriers for stores to objects in the | |
| 264 // young gen and, a fortiori, for initializing stores to | |
| 265 // objects therein. This applies to {DefNew,ParNew}+{Tenured,CMS} | |
| 266 // only and may need to be re-examined in case other | |
| 267 // kinds of collectors are implemented in the future. | |
| 268 virtual bool can_elide_initializing_store_barrier(oop new_obj) { | |
| 269 assert(UseParNewGC || UseSerialGC || UseConcMarkSweepGC, | |
| 270 "Check can_elide_initializing_store_barrier() for this collector"); | |
| 271 return is_in_youngest((void*)new_obj); | |
| 261 } | 272 } |
| 262 | 273 |
| 263 // Can a compiler elide a store barrier when it writes | 274 // Can a compiler elide a store barrier when it writes |
| 264 // a permanent oop into the heap? Applies when the compiler | 275 // a permanent oop into the heap? Applies when the compiler |
| 265 // is storing x to the heap, where x->is_perm() is true. | 276 // is storing x to the heap, where x->is_perm() is true. |