8224814: Remove dead JNIHandleBlock freelist code
Reviewed-by: stefank, tschatzl, kbarrett
--- a/src/hotspot/share/runtime/jniHandles.cpp Mon Jun 03 14:50:59 2019 +0200
+++ b/src/hotspot/share/runtime/jniHandles.cpp Mon Jun 03 13:35:05 2019 +0200
@@ -396,10 +396,8 @@
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 @@
"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 @@
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 @@
current->zap();
}
// Clear initial block
- _free_list = NULL;
- _allocate_before_rebuild = 0;
_last = this;
zap();
}
@@ -514,13 +503,6 @@
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 @@
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]);
--- a/src/hotspot/share/runtime/jniHandles.hpp Mon Jun 03 14:50:59 2019 +0200
+++ b/src/hotspot/share/runtime/jniHandles.hpp Mon Jun 03 13:35:05 2019 +0200
@@ -148,8 +148,6 @@
// 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 @@
// 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; }