进入Eden()->clean()函数
void EdenSpace::clear(bool mangle_space) {
ContiguousSpace::clear(mangle_space);
set_soft_end(end());
}
进入
void ContiguousSpace::clear(bool mangle_space) {
set_top(bottom());
set_saved_mark();
CompactibleSpace::clear(mangle_space);
}
打印对象,这个是eden
(gdb) p this
$154 = (EdenSpace * const) 0x7f4780020328
(gdb) p * this
$155 = (EdenSpace) {
<ContiguousSpace> = {
<CompactibleSpace> = {
<Space> = {
<CHeapObj<1280u>> = {
<AllocatedObj> = {
_vptr.AllocatedObj = 0x7f4788515a90 <vtable for EdenSpace+16>
}, <No data fields>},
members of Space:
_bottom = 0xf3800000,
_end = 0xf5600000,
_saved_mark_word = 0xf4dccdb8,
_preconsumptionDirtyCardClosure = 0x0,
_par_seq_tasks = {
<StackObj> = {
<AllocatedObj> = {
_vptr.AllocatedObj = 0x7f47884fb650 <vtable for SequentialSubTasksDone+16>
}, <No data fields>},
members of SequentialSubTasksDone:
_n_tasks = 0,
_n_claimed = 0,
_n_threads = 0,
_n_completed = 0
}
},
members of CompactibleSpace:
_compaction_top = 0xf3800000,
_next_compaction_space = 0x7f4780020438,
_first_dead = 0xf1f1f1f1f1f1f1f1,
_end_of_live = 0xf1f1f1f1f1f1f1f1
},
members of ContiguousSpace:
_top = 0xf4dccdb8,
_concurrent_iteration_safe_limit = 0xf3800000,
_mangler = 0x7f47800203e8
},
members of EdenSpace:
_gen = 0x7f478001f1c8,
_soft_end = 0xf5600000
}
看实现
(gdb) p bottom() $156 = (HeapWord *) 0xf3800000 (gdb) p top() $157 = (HeapWord *) 0xf4dccdb8
将top清空
设置mark
virtual void set_saved_mark() { _saved_mark_word = top(); }
清理完之后的对象
(gdb) p *this
$159 = (EdenSpace) {
<ContiguousSpace> = {
<CompactibleSpace> = {
<Space> = {
<CHeapObj<1280u>> = {
<AllocatedObj> = {
_vptr.AllocatedObj = 0x7f4788515a90 <vtable for EdenSpace+16>
}, <No data fields>},
members of Space:
_bottom = 0xf3800000,
_end = 0xf5600000,
_saved_mark_word = 0xf3800000,
_preconsumptionDirtyCardClosure = 0x0,
_par_seq_tasks = {
<StackObj> = {
<AllocatedObj> = {
_vptr.AllocatedObj = 0x7f47884fb650 <vtable for SequentialSubTasksDone+16>
}, <No data fields>},
members of SequentialSubTasksDone:
_n_tasks = 0,
_n_claimed = 0,
_n_threads = 0,
_n_completed = 0
}
},
members of CompactibleSpace:
_compaction_top = 0xf3800000,
_next_compaction_space = 0x7f4780020438,
_first_dead = 0xf1f1f1f1f1f1f1f1,
_end_of_live = 0xf1f1f1f1f1f1f1f1
},
members of ContiguousSpace:
_top = 0xf3800000,
_concurrent_iteration_safe_limit = 0xf3800000,
_mangler = 0x7f47800203e8
},
members of EdenSpace:
_gen = 0x7f478001f1c8,
_soft_end = 0xf5600000
}
接着看
CompactibleSpace::clear(mangle_space);
----------------------------------------------
void CompactibleSpace::clear(bool mangle_space) {
Space::clear(mangle_space);
_compaction_top = bottom();
}
----------------------------------------------
void Space::clear(bool mangle_space) {
if (ZapUnusedHeapArea && mangle_space) {
mangle_unused_area();
}
}
-------------------------------------------------
void ContiguousSpace::mangle_unused_area() {
mangler()->mangle_unused_area();
}
-----------------------------------------------------
void SpaceMangler::mangle_unused_area() {
assert(ZapUnusedHeapArea, "Mangling should not be in use");
// Mangle between top and the high water mark. Safeguard
// against the space changing since top_for_allocations was
// set.
HeapWord* mangled_end = MIN2(top_for_allocations(), end());
if (top() < mangled_end) {
MemRegion mangle_mr(top(), mangled_end);
SpaceMangler::mangle_region(mangle_mr);
// Light weight check of mangling.
check_mangled_unused_area(end());
}
// Complete check of unused area which is functional when
// DEBUG_MANGLING is defined.
check_mangled_unused_area_complete();
}
打印这个spaceMangler对象
(gdb) p _mangler
$162 = (GenSpaceMangler *) 0x7f47800203e8
(gdb) p *_mangler
$163 = (GenSpaceMangler) {
<SpaceMangler> = {
<CHeapObj<1280u>> = {
<AllocatedObj> = {
_vptr.AllocatedObj = 0x7f47885163d0 <vtable for GenSpaceMangler+16>
}, <No data fields>},
members of SpaceMangler:
_top_for_allocations = 0xf4dccdb8
},
members of GenSpaceMangler:
_sp = 0x7f4780020328
}
查看紫色函数
(gdb) p end() $164 = (HeapWord *) 0xf5600000 (gdb) p _top_for_allocations $165 = (HeapWord *) 0xf4dccdb8
进入棕色函数
// Simply mangle the MemRegion mr.
void SpaceMangler::mangle_region(MemRegion mr) {
assert(ZapUnusedHeapArea, "Mangling should not be in use");
#ifdef ASSERT
if(TraceZapUnusedHeapArea) {
gclog_or_tty->print("Mangling [0x%x to 0x%x)", mr.start(), mr.end());
}
Copy::fill_to_words(mr.start(), mr.word_size(), badHeapWord);
if(TraceZapUnusedHeapArea) {
gclog_or_tty->print_cr(" done");
}
#endif
}
进入函数
// Fill methods
// Fill word-aligned words, not atomic on each word
// set_words
static void fill_to_words(HeapWord* to, size_t count, juint value = 0) {
assert_params_ok(to, LogHeapWordSize);
pd_fill_to_words(to, count, value);
}
进入
static void pd_fill_to_words(HeapWord* tohw, size_t count, juint value) {
#ifdef AMD64
julong* to = (julong*) tohw;
julong v = ((julong) value << 32) | value;
while (count-- > 0) {
*to++ = v;
}
#else..无用..
#endif // AMD64
}
看badHeapWord的值
(gdb) p/x value $171 = 0xbaadbabe
那么上述过程就是将heap的值全部设置成了0xbaadbabe
接着就是对from区域
(gdb) p from() $175 = (ContiguousSpace *) 0x7f4780020438
重要的交换空间
swap_spaces();
交换之前
(gdb) p this
$181 = (DefNewGeneration * const) 0x7f478001f1c8
(gdb) p* this
$182 = (DefNewGeneration) {
<Generation> = {
<CHeapObj<1280u>> = {
<AllocatedObj> = {
_vptr.AllocatedObj = 0x7f47884ff590 <vtable for DefNewGeneration+16>
}, <No data fields>},
members of Generation:
_time_of_last_gc = -1012762419733073423,
_prev_used_region = {
_start = 0x0,
_word_size = 0
},
_reserved = {
_start = 0xf3800000,
_word_size = 6553600
},
....略部分
_promo_failure_drain_in_progress = false,
_gen_counters = 0x7f4780020638,
_eden_counters = 0x7f478000d678,
_from_counters = 0x7f4780021888,
_to_counters = 0x7f4780021d78,
_max_eden_size = 31457280,
_max_survivor_size = 10485760,
_should_allocate_from_space = false,
_eden_space = 0x7f4780020328,
_from_space = 0x7f4780020438,
_to_space = 0x7f4780020538,
_gc_timer = 0x7f4780022268
}
代码为
void DefNewGeneration::swap_spaces() {
ContiguousSpace* s = from();
_from_space = to();
_to_space = s;
eden()->set_next_compaction_space(from());
// The to-space is normally empty before a compaction so need
// not be considered. The exception is during promotion
// failure handling when to-space can contain live objects.
from()->set_next_compaction_space(NULL);
if (UsePerfData) {
CSpaceCounters* c = _from_counters;
_from_counters = _to_counters;
_to_counters = c;
}
}
这个函数为 eden()->set_next_compaction_space(from());
void set_next_compaction_space(CompactibleSpace* csp) {
_next_compaction_space = csp;
}
将eden()的值设置为新的from值,(即原来的from空间已经变为了to空间)
if (UsePerfData) {
CSpaceCounters* c = _from_counters;
_from_counters = _to_counters;
_to_counters = c;
}
设置完成后就结束了