/**
* 根据统计信息调整当前线程的本地分配缓冲区的基准大小
*/
void ThreadLocalAllocBuffer::resize() {
if (ResizeTLAB) { //允许调整线程的本地分配缓冲区大小
// Compute the next tlab size using expected allocation amount
size_t alloc = (size_t)(_allocation_fraction.average() *
(Universe::heap()->tlab_capacity(myThread()) / HeapWordSize));
size_t new_size = alloc / _target_refills;
//根据本地分配缓冲区大小允许的最大值/最小值来调整缓冲区的新大小
new_size = MIN2(MAX2(new_size, min_size()), max_size());
//内存对齐后的大小
size_t aligned_new_size = align_object_size(new_size);
if (PrintTLAB && Verbose) {
gclog_or_tty->print("TLAB new size: thread: " INTPTR_FORMAT " [id: %2d]"
" refills %d alloc: %8.6f desired_size: " SIZE_FORMAT " -> " SIZE_FORMAT "\n",
myThread(), myThread()->osthread()->thread_id(),
_target_refills, _allocation_fraction.average(), desired_size(), aligned_new_size);
}
set_desired_size(aligned_new_size);
set_refill_waste_limit(initial_refill_waste_limit());
}
}
void ThreadLocalAllocBuffer::fill(HeapWord* start,
HeapWord* top,
size_t new_size) {
_number_of_refills++;
if (PrintTLAB && Verbose) {
print_stats("fill");
}
assert(top <= start + new_size - alignment_reserve(), "size too small");
initialize(start, top, start + new_size - alignment_reserve());
// Reset amount of internal fragmentation
set_refill_waste_limit(initial_refill_waste_limit());
}
void ThreadLocalAllocBuffer::record_slow_allocation(size_t obj_size) {
// Raise size required to bypass TLAB next time. Why? Else there's
// a risk that a thread that repeatedly allocates objects of one
// size will get stuck on this slow path.
set_refill_waste_limit(refill_waste_limit() + refill_waste_limit_increment());
_slow_allocations++;
if (PrintTLAB && Verbose) {
Thread* thrd = myThread();
gclog_or_tty->print("TLAB: %s thread: "INTPTR_FORMAT" [id: %2d]"
" obj: "SIZE_FORMAT
" free: "SIZE_FORMAT
" waste: "SIZE_FORMAT"\n",
"slow", thrd, thrd->osthread()->thread_id(),
obj_size, free(), refill_waste_limit());
}
}
void ThreadLocalAllocBuffer::resize() {
// Compute the next tlab size using expected allocation amount
assert(ResizeTLAB, "Should not call this otherwise");
size_t alloc = (size_t)(_allocation_fraction.average() *
(Universe::heap()->tlab_capacity(myThread()) / HeapWordSize));
size_t new_size = alloc / _target_refills;
new_size = MIN2(MAX2(new_size, min_size()), max_size());
size_t aligned_new_size = align_object_size(new_size);
if (PrintTLAB && Verbose) {
gclog_or_tty->print("TLAB new size: thread: " INTPTR_FORMAT " [id: %2d]"
" refills %d alloc: %8.6f desired_size: " SIZE_FORMAT " -> " SIZE_FORMAT "\n",
p2i(myThread()), myThread()->osthread()->thread_id(),
_target_refills, _allocation_fraction.average(), desired_size(), aligned_new_size);
}
set_desired_size(aligned_new_size);
set_refill_waste_limit(initial_refill_waste_limit());
}
void ThreadLocalAllocBuffer::initialize() {
initialize(NULL, // start
NULL, // top
NULL); // end
set_desired_size(initial_desired_size());
// Following check is needed because at startup the main (primordial)
// thread is initialized before the heap is. The initialization for
// this thread is redone in startup_initialization below.
if (Universe::heap() != NULL) {
size_t capacity = Universe::heap()->tlab_capacity(myThread()) / HeapWordSize;
double alloc_frac = desired_size() * target_refills() / (double) capacity;
_allocation_fraction.sample(alloc_frac);
}
set_refill_waste_limit(initial_refill_waste_limit());
initialize_statistics();
}