/*

 * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

#include "precompiled.hpp"

#include "gc/z/zCPU.inline.hpp"

#include "gc/z/zGlobals.hpp"

#include "gc/z/zHeuristics.hpp"

#include "gc/z/zUtils.inline.hpp"

#include "logging/log.hpp"

#include "runtime/globals.hpp"

#include "runtime/os.hpp"

void ZHeuristics::set_medium_page_size() {

  // Set ZPageSizeMedium so that a medium page occupies at most 3.125% of the

  // max heap size. ZPageSizeMedium is initially set to 0, which means medium

  // pages are effectively disabled. It is adjusted only if ZPageSizeMedium

  // becomes larger than ZPageSizeSmall.

  const size_t min = ZGranuleSize;

  const size_t max = ZGranuleSize * 16;

  const size_t unclamped = MaxHeapSize * 0.03125;

  const size_t clamped = MIN2(MAX2(min, unclamped), max);

  const size_t size = ZUtils::round_down_power_of_2(clamped);

  if (size > ZPageSizeSmall) {

    // Enable medium pages

    ZPageSizeMedium             = size;

    ZPageSizeMediumShift        = log2_intptr(ZPageSizeMedium);

    ZObjectSizeLimitMedium      = ZPageSizeMedium / 8;

    ZObjectAlignmentMediumShift = ZPageSizeMediumShift - 13;

    ZObjectAlignmentMedium      = 1 << ZObjectAlignmentMediumShift;

    log_info(gc, init)("Medium Page Size: " SIZE_FORMAT "M", ZPageSizeMedium / M);

  } else {

    log_info(gc, init)("Medium Page Size: N/A");

  }

}

bool ZHeuristics::use_per_cpu_shared_small_pages() {

  // Use per-CPU shared small pages only if these pages occupy at most 3.125%

  // of the max heap size. Otherwise fall back to using a single shared small

  // page. This is useful when using small heaps on large machines.

  const size_t per_cpu_share = (MaxHeapSize * 0.03125) / ZCPU::count();

  return per_cpu_share >= ZPageSizeSmall;

}