src/hotspot/share/jfr/support/jfrObjectAllocationSample.cpp

/*
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#include "gc/shared/threadLocalAllocBuffer.inline.hpp"
#include "gc/shared/tlab_globals.hpp"
#include "jfr/jfrEvents.hpp"
#include "jfr/support/jfrObjectAllocationSample.hpp"
#include "jfr/support/jfrThreadLocal.hpp"
#include "utilities/globalDefinitions.hpp"

inline bool send_allocation_sample(const Klass* klass, int64_t allocated_bytes, JfrThreadLocal* tl) {
  EventObjectAllocationSample event;
  if (event.should_commit()) {
    const int64_t weight = allocated_bytes - tl->last_allocated_bytes();
    assert(weight > 0, "invariant");
    event.set_objectClass(klass);
    event.set_weight(weight);
    event.commit();
    tl->set_last_allocated_bytes(allocated_bytes);
    return true;
  }
  return false;
}

inline int64_t estimate_tlab_size_bytes(Thread* thread) {
  const size_t desired_tlab_size_bytes = thread->tlab().desired_size() * HeapWordSize;
  const size_t alignment_reserve_bytes = thread->tlab().alignment_reserve_in_bytes();
  assert(desired_tlab_size_bytes >= alignment_reserve_bytes, "invariant");
  return static_cast<int64_t>(desired_tlab_size_bytes - alignment_reserve_bytes);
}

inline int64_t load_allocated_bytes(JfrThreadLocal* tl, Thread* thread) {
  const int64_t allocated_bytes = thread->allocated_bytes();
  return allocated_bytes == tl->last_allocated_bytes() ? 0 : allocated_bytes;
}

// To avoid large objects from being undersampled compared to the regular TLAB samples,
// the data amount is normalized as if it was a TLAB, giving a number of TLAB sampling attempts to the large object.
static void normalize_as_tlab_and_send_allocation_samples(const Klass* klass, int64_t obj_alloc_size_bytes, JfrThreadLocal* tl, Thread* thread) {
  const int64_t allocated_bytes = load_allocated_bytes(tl, thread);
  assert(allocated_bytes > 0, "invariant"); // obj_alloc_size_bytes is already attributed to allocated_bytes at this point.
  if (!UseTLAB) {
    send_allocation_sample(klass, allocated_bytes, tl);
    return;
  }
  const int64_t tlab_size_bytes = estimate_tlab_size_bytes(thread);
  if (tlab_size_bytes <= 0) {
    // We don't get a TLAB, avoid endless loop below.
    return;
  }
  if (allocated_bytes - tl->last_allocated_bytes() < tlab_size_bytes) {
    return;
  }
  assert(obj_alloc_size_bytes > 0, "invariant");
  do {
    if (send_allocation_sample(klass, allocated_bytes, tl)) {
      return;
    }
    obj_alloc_size_bytes -= tlab_size_bytes;
  } while (obj_alloc_size_bytes > 0);
}

void JfrObjectAllocationSample::send_event(const Klass* klass, size_t alloc_size, bool outside_tlab, Thread* thread) {
  assert(thread != nullptr, "invariant");
  JfrThreadLocal* const tl = thread->jfr_thread_local();
  assert(tl != nullptr, "invariant");
  if (outside_tlab) {
    normalize_as_tlab_and_send_allocation_samples(klass, static_cast<int64_t>(alloc_size), tl, thread);
    return;
  }
  const int64_t allocated_bytes = load_allocated_bytes(tl, thread);
  if (allocated_bytes == 0) {
    return;
  }
  send_allocation_sample(klass, allocated_bytes, tl);
}