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8224814: Remove dead JNIHandleBlock freelist code

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Reviewed-by: stefank, tschatzl, kbarrett
This commit is contained in:
Erik Österlund 2019-06-03 13:35:05 +02:00
parent d25350462e
commit 50e2aa7306
2 changed files with 9 additions and 67 deletions
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71
src/hotspot/share/runtime/jniHandles.cpp
View File

@ -396,10 +396,8 @@ JNIHandleBlock* JNIHandleBlock::allocate_block(Thread* thread) {
block->_next = NULL;
block->_pop_frame_link = NULL;
block->_planned_capacity = block_size_in_oops;
// _last, _free_list & _allocate_before_rebuild initialized in allocate_handle
// _last initialized in allocate_handle
debug_only(block->_last = NULL);
debug_only(block->_free_list = NULL);
debug_only(block->_allocate_before_rebuild = -1);
return block;
}
@ -460,12 +458,7 @@ void JNIHandleBlock::oops_do(OopClosure* f) {
"only blocks first in chain should have pop frame link set");
for (int index = 0; index < current->_top; index++) {
oop* root = &(current->_handles)[index];
oop value = *root;
// traverse heap pointers only, not deleted handles or free list
// pointers
if (value != NULL && Universe::heap()->is_in_reserved(value)) {
f->do_oop(root);
}
f->do_oop(root);
}
// the next handle block is valid only if current block is full
if (current->_top < block_size_in_oops) {
@ -486,8 +479,6 @@ jobject JNIHandleBlock::allocate_handle(oop obj) {
for (JNIHandleBlock* current = _next; current != NULL;
current = current->_next) {
assert(current->_last == NULL, "only first block should have _last set");
assert(current->_free_list == NULL,
"only first block should have _free_list set");
if (current->_top == 0) {
// All blocks after the first clear trailing block are already cleared.
#ifdef ASSERT
@ -501,8 +492,6 @@ jobject JNIHandleBlock::allocate_handle(oop obj) {
current->zap();
}
// Clear initial block
_free_list = NULL;
_allocate_before_rebuild = 0;
_last = this;
zap();
}
@ -514,13 +503,6 @@ jobject JNIHandleBlock::allocate_handle(oop obj) {
return (jobject) handle;
}
// Try free list
if (_free_list != NULL) {
oop* handle = _free_list;
_free_list = (oop*) *_free_list;
NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj);
return (jobject) handle;
}
// Check if unused block follow last
if (_last->_next != NULL) {
// update last and retry
@ -528,51 +510,16 @@ jobject JNIHandleBlock::allocate_handle(oop obj) {
return allocate_handle(obj);
}
// No space available, we have to rebuild free list or expand
if (_allocate_before_rebuild == 0) {
rebuild_free_list(); // updates _allocate_before_rebuild counter
} else {
// Append new block
Thread* thread = Thread::current();
Handle obj_handle(thread, obj);
// This can block, so we need to preserve obj across call.
_last->_next = JNIHandleBlock::allocate_block(thread);
_last = _last->_next;
_allocate_before_rebuild--;
obj = obj_handle();
}
// Append new block
Thread* thread = Thread::current();
Handle obj_handle(thread, obj);
// This can block, so we need to preserve obj across call.
_last->_next = JNIHandleBlock::allocate_block(thread);
_last = _last->_next;
obj = obj_handle();
return allocate_handle(obj); // retry
}
void JNIHandleBlock::rebuild_free_list() {
assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking");
int free = 0;
int blocks = 0;
for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
for (int index = 0; index < current->_top; index++) {
oop* handle = &(current->_handles)[index];
if (*handle == NULL) {
// this handle was cleared out by a delete call, reuse it
*handle = (oop) _free_list;
_free_list = handle;
free++;
}
}
// we should not rebuild free list if there are unused handles at the end
assert(current->_top == block_size_in_oops, "just checking");
blocks++;
}
// Heuristic: if more than half of the handles are free we rebuild next time
// as well, otherwise we append a corresponding number of new blocks before
// attempting a free list rebuild again.
int total = blocks * block_size_in_oops;
int extra = total - 2*free;
if (extra > 0) {
// Not as many free handles as we would like - compute number of new blocks to append
_allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops;
}
}
bool JNIHandleBlock::contains(jobject handle) const {
return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]);

5
src/hotspot/share/runtime/jniHandles.hpp
View File

@ -148,8 +148,6 @@ class JNIHandleBlock : public CHeapObj<mtInternal> {
// Having two types of blocks complicates the code and the space overhead in negligible.
JNIHandleBlock* _last; // Last block in use
JNIHandleBlock* _pop_frame_link; // Block to restore on PopLocalFrame call
oop* _free_list; // Handle free list
int _allocate_before_rebuild; // Number of blocks to allocate before rebuilding free list
// Check JNI, "planned capacity" for current frame (or push/ensure)
size_t _planned_capacity;
@ -165,9 +163,6 @@ class JNIHandleBlock : public CHeapObj<mtInternal> {
// Fill block with bad_handle values
void zap() NOT_DEBUG_RETURN;
// Free list computation
void rebuild_free_list();
// No more handles in the both the current and following blocks
void clear() { _top = 0; }