8333641: Serial: Remove Generation::supports_tlab_allocation

Reviewed-by: tschatzl

Author: albertnetymk

src/hotspot/share/gc/serial/defNewGeneration.hpp

@@ -191,7 +191,6 @@ class DefNewGeneration: public Generation {
   size_t max_survivor_size() const          { return _max_survivor_size; }
 
   // Thread-local allocation buffers
-  bool supports_tlab_allocation() const { return true; }
   size_t tlab_capacity() const;
   size_t tlab_used() const;
   size_t unsafe_max_tlab_alloc() const;

src/hotspot/share/gc/serial/generation.hpp

@@ -114,9 +114,6 @@ class Generation: public CHeapObj<mtGC> {
   // Like "allocate", but performs any necessary locking internally.
   virtual HeapWord* par_allocate(size_t word_size, bool is_tlab) = 0;
 
-  // Thread-local allocation buffers
-  virtual bool supports_tlab_allocation() const { return false; }
-
   // Perform a heap collection, attempting to create (at least) enough
   // space to support an allocation of the given "word_size".  If
   // successful, perform the allocation and return the resulting

src/hotspot/share/gc/serial/serialHeap.cpp

@@ -833,20 +833,15 @@ bool SerialHeap::block_is_obj(const HeapWord* addr) const {
 }
 
 size_t SerialHeap::tlab_capacity(Thread* thr) const {
-  assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
-  assert(_young_gen->supports_tlab_allocation(), "Young gen doesn't support TLAB allocation?!");
+  // Only young-gen supports tlab allocation.
   return _young_gen->tlab_capacity();
 }
 
 size_t SerialHeap::tlab_used(Thread* thr) const {
-  assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
-  assert(_young_gen->supports_tlab_allocation(), "Young gen doesn't support TLAB allocation?!");
   return _young_gen->tlab_used();
 }
 
 size_t SerialHeap::unsafe_max_tlab_alloc(Thread* thr) const {
-  assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
-  assert(_young_gen->supports_tlab_allocation(), "Young gen doesn't support TLAB allocation?!");
   return _young_gen->unsafe_max_tlab_alloc();
 }
 

src/hotspot/share/gc/serial/tenuredGeneration.hpp

@@ -143,7 +143,7 @@ class TenuredGeneration: public Generation {
   bool should_allocate(size_t word_size, bool is_tlab) {
     bool result = false;
     size_t overflow_limit = (size_t)1 << (BitsPerSize_t - LogHeapWordSize);
-    if (!is_tlab || supports_tlab_allocation()) {
+    if (!is_tlab) {
       result = (word_size > 0) && (word_size < overflow_limit);
     }
     return result;