jdk-24/test/hotspot/gtest/runtime/test_os.cpp

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
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 *
 * 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.
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#include "precompiled.hpp"
#include "runtime/os.hpp"
#include "unittest.hpp"

static size_t small_page_size() {
  return os::vm_page_size();
}

static size_t large_page_size() {
  const size_t large_page_size_example = 4 * M;
  return os::page_size_for_region_aligned(large_page_size_example, 1);
}

TEST_VM(os, page_size_for_region) {
  size_t large_page_example = 4 * M;
  size_t large_page = os::page_size_for_region_aligned(large_page_example, 1);

  size_t small_page = os::vm_page_size();
  if (large_page > small_page) {
    size_t num_small_in_large = large_page / small_page;
    size_t page = os::page_size_for_region_aligned(large_page, num_small_in_large);
    ASSERT_EQ(page, small_page) << "Did not get a small page";
  }
}

TEST_VM(os, page_size_for_region_aligned) {
  if (UseLargePages) {
    const size_t small_page = small_page_size();
    const size_t large_page = large_page_size();

    if (large_page > small_page) {
      size_t num_small_pages_in_large = large_page / small_page;
      size_t page = os::page_size_for_region_aligned(large_page, num_small_pages_in_large);

      ASSERT_EQ(page, small_page);
    }
  }
}

TEST_VM(os, page_size_for_region_alignment) {
  if (UseLargePages) {
    const size_t small_page = small_page_size();
    const size_t large_page = large_page_size();
    if (large_page > small_page) {
      const size_t unaligned_region = large_page + 17;
      size_t page = os::page_size_for_region_aligned(unaligned_region, 1);
      ASSERT_EQ(page, small_page);

      const size_t num_pages = 5;
      const size_t aligned_region = large_page * num_pages;
      page = os::page_size_for_region_aligned(aligned_region, num_pages);
      ASSERT_EQ(page, large_page);
    }
  }
}

TEST_VM(os, page_size_for_region_unaligned) {
  if (UseLargePages) {
    // Given exact page size, should return that page size.
    for (size_t i = 0; os::_page_sizes[i] != 0; i++) {
      size_t expected = os::_page_sizes[i];
      size_t actual = os::page_size_for_region_unaligned(expected, 1);
      ASSERT_EQ(expected, actual);
    }

    // Given slightly larger size than a page size, return the page size.
    for (size_t i = 0; os::_page_sizes[i] != 0; i++) {
      size_t expected = os::_page_sizes[i];
      size_t actual = os::page_size_for_region_unaligned(expected + 17, 1);
      ASSERT_EQ(expected, actual);
    }

    // Given a slightly smaller size than a page size,
    // return the next smaller page size.
    if (os::_page_sizes[1] > os::_page_sizes[0]) {
      size_t expected = os::_page_sizes[0];
      size_t actual = os::page_size_for_region_unaligned(os::_page_sizes[1] - 17, 1);
      ASSERT_EQ(actual, expected);
    }

    // Return small page size for values less than a small page.
    size_t small_page = small_page_size();
    size_t actual = os::page_size_for_region_unaligned(small_page - 17, 1);
    ASSERT_EQ(small_page, actual);
  }
}

TEST(os, test_random) {
  const double m = 2147483647;
  double mean = 0.0, variance = 0.0, t;
  const int reps = 10000;
  unsigned int seed = 1;

  // tty->print_cr("seed %ld for %ld repeats...", seed, reps);
  os::init_random(seed);
  int num;
  for (int k = 0; k < reps; k++) {
    num = os::random();
    double u = (double)num / m;
    ASSERT_TRUE(u >= 0.0 && u <= 1.0) << "bad random number!";

    // calculate mean and variance of the random sequence
    mean += u;
    variance += (u*u);
  }
  mean /= reps;
  variance /= (reps - 1);

  ASSERT_EQ(num, 1043618065) << "bad seed";
  // tty->print_cr("mean of the 1st 10000 numbers: %f", mean);
  int intmean = mean*100;
  ASSERT_EQ(intmean, 50);
  // tty->print_cr("variance of the 1st 10000 numbers: %f", variance);
  int intvariance = variance*100;
  ASSERT_EQ(intvariance, 33);
  const double eps = 0.0001;
  t = fabsd(mean - 0.5018);
  ASSERT_LT(t, eps) << "bad mean";
  t = (variance - 0.3355) < 0.0 ? -(variance - 0.3355) : variance - 0.3355;
  ASSERT_LT(t, eps) << "bad variance";
}


#ifdef ASSERT
TEST_VM_ASSERT_MSG(os, page_size_for_region_with_zero_min_pages, "sanity") {
  size_t region_size = 16 * os::vm_page_size();
  os::page_size_for_region_aligned(region_size, 0); // should assert
}
#endif