6977804: G1: remove the zero-filling thread
Summary: This changeset removes the zero-filling thread from G1 and collapses the two free region lists we had before (the "free" and "unclean" lists) into one. The new free list uses the new heap region sets / lists abstractions that we'll ultimately use it to keep track of all regions in the heap. A heap region set was also introduced for the humongous regions. Finally, this change increases the concurrency between the thread that completes freeing regions (after a cleanup pause) and the rest of the system (before we'd have to wait for said thread to complete before allocating a new region). The changest also includes a lot of refactoring and code simplification.
Reviewed-by: jcoomes, johnc
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#include "precompiled.hpp"
#include "gc_implementation/g1/heapRegionSets.hpp"
//////////////////// FreeRegionList ////////////////////
const char* FreeRegionList::verify_region_extra(HeapRegion* hr) {
if (hr->is_young()) {
return "the region should not be young";
}
// The superclass will check that the region is empty and
// not-humongous.
return HeapRegionLinkedList::verify_region_extra(hr);
}
//////////////////// MasterFreeRegionList ////////////////////
bool MasterFreeRegionList::check_mt_safety() {
// Master Free List MT safety protocol:
// (a) If we're at a safepoint, operations on the master free list
// should be invoked by either the VM thread (which will serialize
// them) or by the GC workers while holding the
// FreeList_lock.
// (b) If we're not at a safepoint, operations on the master free
// list should be invoked while holding the Heap_lock.
guarantee((SafepointSynchronize::is_at_safepoint() &&
(Thread::current()->is_VM_thread() ||
FreeList_lock->owned_by_self())) ||
(!SafepointSynchronize::is_at_safepoint() &&
Heap_lock->owned_by_self()),
hrl_ext_msg(this, "master free list MT safety protocol"));
return FreeRegionList::check_mt_safety();
}
//////////////////// SecondaryFreeRegionList ////////////////////
bool SecondaryFreeRegionList::check_mt_safety() {
// Secondary Free List MT safety protocol:
// Operations on the secondary free list should always be invoked
// while holding the SecondaryFreeList_lock.
guarantee(SecondaryFreeList_lock->owned_by_self(),
hrl_ext_msg(this, "secondary free list MT safety protocol"));
return FreeRegionList::check_mt_safety();
}
//////////////////// HumongousRegionSet ////////////////////
const char* HumongousRegionSet::verify_region_extra(HeapRegion* hr) {
if (hr->is_young()) {
return "the region should not be young";
}
// The superclass will check that the region is not empty and
// humongous.
return HeapRegionSet::verify_region_extra(hr);
}
//////////////////// HumongousRegionSet ////////////////////
bool MasterHumongousRegionSet::check_mt_safety() {
// Master Humongous Set MT safety protocol:
// (a) If we're at a safepoint, operations on the master humongous
// set should be invoked by either the VM thread (which will
// serialize them) or by the GC workers while holding the
// OldSets_lock.
// (b) If we're not at a safepoint, operations on the master
// humongous set should be invoked while holding the Heap_lock.
guarantee((SafepointSynchronize::is_at_safepoint() &&
(Thread::current()->is_VM_thread() ||
OldSets_lock->owned_by_self())) ||
(!SafepointSynchronize::is_at_safepoint() &&
Heap_lock->owned_by_self()),
hrl_ext_msg(this, "master humongous set MT safety protocol"));
return HumongousRegionSet::check_mt_safety();
}