Initial checkin of gRPC to third_party/

third_party/grpc/test/core/statistics/census_log_tests.c

Index: third_party/grpc/test/core/statistics/census_log_tests.c
diff --git a/third_party/grpc/test/core/statistics/census_log_tests.c b/third_party/grpc/test/core/statistics/census_log_tests.c
new file mode 100644
index 0000000000000000000000000000000000000000..77cc57d4d63b75ea050fd08873d136e7a11a4c69
--- /dev/null
+++ b/third_party/grpc/test/core/statistics/census_log_tests.c
@@ -0,0 +1,591 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/statistics/census_log.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <grpc/support/cpu.h>
+#include <grpc/support/log.h>
+#include <grpc/support/port_platform.h>
+#include <grpc/support/sync.h>
+#include <grpc/support/thd.h>
+#include <grpc/support/time.h>
+#include <grpc/support/useful.h>
+#include "test/core/util/test_config.h"
+
+/* Fills in 'record' of size 'size'. Each byte in record is filled in with the
+   same value. The value is extracted from 'record' pointer. */
+static void write_record(char *record, size_t size) {
+  char data = (uintptr_t)record % 255;
+  memset(record, data, size);
+}
+
+/* Reads fixed size records. Returns the number of records read in
+   'num_records'. */
+static void read_records(size_t record_size, const char *buffer,
+                         size_t buffer_size, int32_t *num_records) {
+  int32_t ix;
+  GPR_ASSERT(buffer_size >= record_size);
+  GPR_ASSERT(buffer_size % record_size == 0);
+  *num_records = buffer_size / record_size;
+  for (ix = 0; ix < *num_records; ++ix) {
+    size_t jx;
+    const char *record = buffer + (record_size * ix);
+    char data = (uintptr_t)record % 255;
+    for (jx = 0; jx < record_size; ++jx) {
+      GPR_ASSERT(data == record[jx]);
+    }
+  }
+}
+
+/* Tries to write the specified number of records. Stops when the log gets
+   full. Returns the number of records written. Spins for random
+   number of times, up to 'max_spin_count', between writes. */
+static size_t write_records_to_log(int writer_id, int32_t record_size,
+                                   int32_t num_records,
+                                   int32_t max_spin_count) {
+  int32_t ix;
+  int counter = 0;
+  for (ix = 0; ix < num_records; ++ix) {
+    int32_t jx;
+    int32_t spin_count = max_spin_count ? rand() % max_spin_count : 0;
+    char *record;
+    if (counter++ == num_records / 10) {
+      printf("   Writer %d: %d out of %d written\n", writer_id, ix,
+             num_records);
+      counter = 0;
+    }
+    record = (char *)(census_log_start_write(record_size));
+    if (record == NULL) {
+      return ix;
+    }
+    write_record(record, record_size);
+    census_log_end_write(record, record_size);
+    for (jx = 0; jx < spin_count; ++jx) {
+      GPR_ASSERT(jx >= 0);
+    }
+  }
+  return num_records;
+}
+
+/* Performs a single read iteration. Returns the number of records read. */
+static size_t perform_read_iteration(size_t record_size) {
+  const void *read_buffer = NULL;
+  size_t bytes_available;
+  size_t records_read = 0;
+  census_log_init_reader();
+  while ((read_buffer = census_log_read_next(&bytes_available))) {
+    int32_t num_records = 0;
+    read_records(record_size, (const char *)read_buffer, bytes_available,
+                 &num_records);
+    records_read += num_records;
+  }
+  return records_read;
+}
+
+/* Asserts that the log is empty. */
+static void assert_log_empty(void) {
+  size_t bytes_available;
+  census_log_init_reader();
+  GPR_ASSERT(census_log_read_next(&bytes_available) == NULL);
+}
+
+/* Given log size and record size, computes the minimum usable space. */
+static int32_t min_usable_space(size_t log_size, size_t record_size) {
+  int32_t usable_space;
+  int32_t num_blocks =
+      GPR_MAX(log_size / CENSUS_LOG_MAX_RECORD_SIZE, gpr_cpu_num_cores());
+  int32_t waste_per_block = CENSUS_LOG_MAX_RECORD_SIZE % record_size;
+  /* In the worst case, all except one core-local block is full. */
+  int32_t num_full_blocks = num_blocks - 1;
+  usable_space = (int32_t)log_size -
+                 (num_full_blocks * CENSUS_LOG_MAX_RECORD_SIZE) -
+                 ((num_blocks - num_full_blocks) * waste_per_block);
+  GPR_ASSERT(usable_space > 0);
+  return usable_space;
+}
+
+/* Fills the log and verifies data. If 'no fragmentation' is true, records
+   are sized such that CENSUS_LOG_2_MAX_RECORD_SIZE is a multiple of record
+   size. If not a circular log, verifies that the number of records written
+   match the number of records read. */
+static void fill_log(size_t log_size, int no_fragmentation, int circular_log) {
+  int size;
+  int32_t records_written;
+  int32_t usable_space;
+  int32_t records_read;
+  if (no_fragmentation) {
+    int log2size = rand() % (CENSUS_LOG_2_MAX_RECORD_SIZE + 1);
+    size = (1 << log2size);
+  } else {
+    while (1) {
+      size = 1 + (rand() % CENSUS_LOG_MAX_RECORD_SIZE);
+      if (CENSUS_LOG_MAX_RECORD_SIZE % size) {
+        break;
+      }
+    }
+  }
+  printf("   Fill record size: %d\n", size);
+  records_written = write_records_to_log(
+      0 /* writer id */, size, (log_size / size) * 2, 0 /* spin count */);
+  usable_space = min_usable_space(log_size, size);
+  GPR_ASSERT(records_written * size >= usable_space);
+  records_read = perform_read_iteration(size);
+  if (!circular_log) {
+    GPR_ASSERT(records_written == records_read);
+  }
+  assert_log_empty();
+}
+
+/* Structure to pass args to writer_thread */
+typedef struct writer_thread_args {
+  /* Index of this thread in the writers vector. */
+  int index;
+  /* Record size. */
+  size_t record_size;
+  /* Number of records to write. */
+  int32_t num_records;
+  /* Used to signal when writer is complete */
+  gpr_cv *done;
+  gpr_mu *mu;
+  int *count;
+} writer_thread_args;
+
+/* Writes the given number of records of random size (up to kMaxRecordSize) and
+   random data to the specified log. */
+static void writer_thread(void *arg) {
+  writer_thread_args *args = (writer_thread_args *)arg;
+  /* Maximum number of times to spin between writes. */
+  static const int32_t MAX_SPIN_COUNT = 50;
+  int records_written = 0;
+  printf("   Writer: %d\n", args->index);
+  while (records_written < args->num_records) {
+    records_written += write_records_to_log(args->index, args->record_size,
+                                            args->num_records - records_written,
+                                            MAX_SPIN_COUNT);
+    if (records_written < args->num_records) {
+      /* Ran out of log space. Sleep for a bit and let the reader catch up.
+         This should never happen for circular logs. */
+      printf("   Writer stalled due to out-of-space: %d out of %d written\n",
+             records_written, args->num_records);
+      gpr_sleep_until(GRPC_TIMEOUT_MILLIS_TO_DEADLINE(10));
+    }
+  }
+  /* Done. Decrement count and signal. */
+  gpr_mu_lock(args->mu);
+  (*args->count)--;
+  gpr_cv_broadcast(args->done);
+  printf("   Writer done: %d\n", args->index);
+  gpr_mu_unlock(args->mu);
+}
+
+/* struct to pass args to reader_thread */
+typedef struct reader_thread_args {
+  /* Record size. */
+  size_t record_size;
+  /* Interval between read iterations. */
+  int32_t read_iteration_interval_in_msec;
+  /* Total number of records. */
+  int32_t total_records;
+  /* Signalled when reader should stop. */
+  gpr_cv stop;
+  int stop_flag;
+  /* Used to signal when reader has finished */
+  gpr_cv *done;
+  gpr_mu *mu;
+  int running;
+} reader_thread_args;
+
+/* Reads and verifies the specified number of records. Reader can also be
+   stopped via gpr_cv_signal(&args->stop). Sleeps for 'read_interval_in_msec'
+   between read iterations. */
+static void reader_thread(void *arg) {
+  int32_t records_read = 0;
+  reader_thread_args *args = (reader_thread_args *)arg;
+  int32_t num_iterations = 0;
+  gpr_timespec interval;
+  int counter = 0;
+  printf("   Reader starting\n");
+  interval = gpr_time_from_micros(
+      (int64_t)args->read_iteration_interval_in_msec * 1000, GPR_TIMESPAN);
+  gpr_mu_lock(args->mu);
+  while (!args->stop_flag && records_read < args->total_records) {
+    gpr_cv_wait(&args->stop, args->mu, interval);
+    if (!args->stop_flag) {
+      records_read += perform_read_iteration(args->record_size);
+      GPR_ASSERT(records_read <= args->total_records);
+      if (counter++ == 100000) {
+        printf("   Reader: %d out of %d read\n", records_read,
+               args->total_records);
+        counter = 0;
+      }
+      ++num_iterations;
+    }
+  }
+  /* Done */
+  args->running = 0;
+  gpr_cv_broadcast(args->done);
+  printf("   Reader: records: %d, iterations: %d\n", records_read,
+         num_iterations);
+  gpr_mu_unlock(args->mu);
+}
+
+/* Creates NUM_WRITERS writers where each writer writes NUM_RECORDS_PER_WRITER
+   records. Also, starts a reader that iterates over and reads blocks every
+   READ_ITERATION_INTERVAL_IN_MSEC. */
+/* Number of writers. */
+#define NUM_WRITERS 5
+static void multiple_writers_single_reader(int circular_log) {
+  /* Sleep interval between read iterations. */
+  static const int32_t READ_ITERATION_INTERVAL_IN_MSEC = 10;
+  /* Number of records written by each writer. */
+  static const int32_t NUM_RECORDS_PER_WRITER = 10 * 1024 * 1024;
+  /* Maximum record size. */
+  static const size_t MAX_RECORD_SIZE = 10;
+  int ix;
+  gpr_thd_id id;
+  gpr_cv writers_done;
+  int writers_count = NUM_WRITERS;
+  gpr_mu writers_mu; /* protects writers_done and writers_count */
+  writer_thread_args writers[NUM_WRITERS];
+  gpr_cv reader_done;
+  gpr_mu reader_mu; /* protects reader_done and reader.running */
+  reader_thread_args reader;
+  int32_t record_size = 1 + rand() % MAX_RECORD_SIZE;
+  printf("   Record size: %d\n", record_size);
+  /* Create and start writers. */
+  gpr_cv_init(&writers_done);
+  gpr_mu_init(&writers_mu);
+  for (ix = 0; ix < NUM_WRITERS; ++ix) {
+    writers[ix].index = ix;
+    writers[ix].record_size = record_size;
+    writers[ix].num_records = NUM_RECORDS_PER_WRITER;
+    writers[ix].done = &writers_done;
+    writers[ix].count = &writers_count;
+    writers[ix].mu = &writers_mu;
+    gpr_thd_new(&id, &writer_thread, &writers[ix], NULL);
+  }
+  /* Start reader. */
+  reader.record_size = record_size;
+  reader.read_iteration_interval_in_msec = READ_ITERATION_INTERVAL_IN_MSEC;
+  reader.total_records = NUM_WRITERS * NUM_RECORDS_PER_WRITER;
+  reader.stop_flag = 0;
+  gpr_cv_init(&reader.stop);
+  gpr_cv_init(&reader_done);
+  reader.done = &reader_done;
+  gpr_mu_init(&reader_mu);
+  reader.mu = &reader_mu;
+  reader.running = 1;
+  gpr_thd_new(&id, &reader_thread, &reader, NULL);
+  /* Wait for writers to finish. */
+  gpr_mu_lock(&writers_mu);
+  while (writers_count != 0) {
+    gpr_cv_wait(&writers_done, &writers_mu, gpr_inf_future(GPR_CLOCK_REALTIME));
+  }
+  gpr_mu_unlock(&writers_mu);
+  gpr_mu_destroy(&writers_mu);
+  gpr_cv_destroy(&writers_done);
+  gpr_mu_lock(&reader_mu);
+  if (circular_log) {
+    /* Stop reader. */
+    reader.stop_flag = 1;
+    gpr_cv_signal(&reader.stop);
+  }
+  /* wait for reader to finish */
+  while (reader.running) {
+    gpr_cv_wait(&reader_done, &reader_mu, gpr_inf_future(GPR_CLOCK_REALTIME));
+  }
+  if (circular_log) {
+    /* Assert that there were no out-of-space errors. */
+    GPR_ASSERT(0 == census_log_out_of_space_count());
+  }
+  gpr_mu_unlock(&reader_mu);
+  gpr_mu_destroy(&reader_mu);
+  gpr_cv_destroy(&reader_done);
+  printf("   Reader: finished\n");
+}
+
+/* Log sizes to use for all tests. */
+#define LOG_SIZE_IN_MB 1
+#define LOG_SIZE_IN_BYTES (LOG_SIZE_IN_MB << 20)
+
+static void setup_test(int circular_log) {
+  census_log_initialize(LOG_SIZE_IN_MB, circular_log);
+  GPR_ASSERT(census_log_remaining_space() == LOG_SIZE_IN_BYTES);
+}
+
+/* Attempts to create a record of invalid size (size >
+   CENSUS_LOG_MAX_RECORD_SIZE). */
+void test_invalid_record_size(void) {
+  static const size_t INVALID_SIZE = CENSUS_LOG_MAX_RECORD_SIZE + 1;
+  static const size_t VALID_SIZE = 1;
+  void *record;
+  printf("Starting test: invalid record size\n");
+  setup_test(0);
+  record = census_log_start_write(INVALID_SIZE);
+  GPR_ASSERT(record == NULL);
+  /* Now try writing a valid record. */
+  record = census_log_start_write(VALID_SIZE);
+  GPR_ASSERT(record != NULL);
+  census_log_end_write(record, VALID_SIZE);
+  /* Verifies that available space went down by one block. In theory, this
+     check can fail if the thread is context switched to a new CPU during the
+     start_write execution (multiple blocks get allocated), but this has not
+     been observed in practice. */
+  GPR_ASSERT(LOG_SIZE_IN_BYTES - CENSUS_LOG_MAX_RECORD_SIZE ==
+             census_log_remaining_space());
+  census_log_shutdown();
+}
+
+/* Tests end_write() with a different size than what was specified in
+   start_write(). */
+void test_end_write_with_different_size(void) {
+  static const size_t START_WRITE_SIZE = 10;
+  static const size_t END_WRITE_SIZE = 7;
+  void *record_written;
+  const void *record_read;
+  size_t bytes_available;
+  printf("Starting test: end write with different size\n");
+  setup_test(0);
+  record_written = census_log_start_write(START_WRITE_SIZE);
+  GPR_ASSERT(record_written != NULL);
+  census_log_end_write(record_written, END_WRITE_SIZE);
+  census_log_init_reader();
+  record_read = census_log_read_next(&bytes_available);
+  GPR_ASSERT(record_written == record_read);
+  GPR_ASSERT(END_WRITE_SIZE == bytes_available);
+  assert_log_empty();
+  census_log_shutdown();
+}
+
+/* Verifies that pending records are not available via read_next(). */
+void test_read_pending_record(void) {
+  static const size_t PR_RECORD_SIZE = 1024;
+  size_t bytes_available;
+  const void *record_read;
+  void *record_written;
+  printf("Starting test: read pending record\n");
+  setup_test(0);
+  /* Start a write. */
+  record_written = census_log_start_write(PR_RECORD_SIZE);
+  GPR_ASSERT(record_written != NULL);
+  /* As write is pending, read should fail. */
+  census_log_init_reader();
+  record_read = census_log_read_next(&bytes_available);
+  GPR_ASSERT(record_read == NULL);
+  /* A read followed by end_write() should succeed. */
+  census_log_end_write(record_written, PR_RECORD_SIZE);
+  census_log_init_reader();
+  record_read = census_log_read_next(&bytes_available);
+  GPR_ASSERT(record_written == record_read);
+  GPR_ASSERT(PR_RECORD_SIZE == bytes_available);
+  assert_log_empty();
+  census_log_shutdown();
+}
+
+/* Tries reading beyond pending write. */
+void test_read_beyond_pending_record(void) {
+  /* Start a write. */
+  uint32_t incomplete_record_size = 10;
+  uint32_t complete_record_size = 20;
+  size_t bytes_available;
+  void *complete_record;
+  const void *record_read;
+  void *incomplete_record;
+  printf("Starting test: read beyond pending record\n");
+  setup_test(0);
+  incomplete_record = census_log_start_write(incomplete_record_size);
+  GPR_ASSERT(incomplete_record != NULL);
+  complete_record = census_log_start_write(complete_record_size);
+  GPR_ASSERT(complete_record != NULL);
+  GPR_ASSERT(complete_record != incomplete_record);
+  census_log_end_write(complete_record, complete_record_size);
+  /* Now iterate over blocks to read completed records. */
+  census_log_init_reader();
+  record_read = census_log_read_next(&bytes_available);
+  GPR_ASSERT(complete_record == record_read);
+  GPR_ASSERT(complete_record_size == bytes_available);
+  /* Complete first record. */
+  census_log_end_write(incomplete_record, incomplete_record_size);
+  /* Have read past the incomplete record, so read_next() should return NULL. */
+  /* NB: this test also assumes our thread did not get switched to a different
+     CPU between the two start_write calls */
+  record_read = census_log_read_next(&bytes_available);
+  GPR_ASSERT(record_read == NULL);
+  /* Reset reader to get the newly completed record. */
+  census_log_init_reader();
+  record_read = census_log_read_next(&bytes_available);
+  GPR_ASSERT(incomplete_record == record_read);
+  GPR_ASSERT(incomplete_record_size == bytes_available);
+  assert_log_empty();
+  census_log_shutdown();
+}
+
+/* Tests scenario where block being read is detached from a core and put on the
+   dirty list. */
+void test_detached_while_reading(void) {
+  static const size_t DWR_RECORD_SIZE = 10;
+  size_t bytes_available;
+  const void *record_read;
+  void *record_written;
+  uint32_t block_read = 0;
+  printf("Starting test: detached while reading\n");
+  setup_test(0);
+  /* Start a write. */
+  record_written = census_log_start_write(DWR_RECORD_SIZE);
+  GPR_ASSERT(record_written != NULL);
+  census_log_end_write(record_written, DWR_RECORD_SIZE);
+  /* Read this record. */
+  census_log_init_reader();
+  record_read = census_log_read_next(&bytes_available);
+  GPR_ASSERT(record_read != NULL);
+  GPR_ASSERT(DWR_RECORD_SIZE == bytes_available);
+  /* Now fill the log. This will move the block being read from core-local
+     array to the dirty list. */
+  while ((record_written = census_log_start_write(DWR_RECORD_SIZE))) {
+    census_log_end_write(record_written, DWR_RECORD_SIZE);
+  }
+
+  /* In this iteration, read_next() should only traverse blocks in the
+     core-local array. Therefore, we expect at most gpr_cpu_num_cores() more
+     blocks. As log is full, if read_next() is traversing the dirty list, we
+     will get more than gpr_cpu_num_cores() blocks. */
+  while ((record_read = census_log_read_next(&bytes_available))) {
+    ++block_read;
+    GPR_ASSERT(block_read <= gpr_cpu_num_cores());
+  }
+  census_log_shutdown();
+}
+
+/* Fills non-circular log with records sized such that size is a multiple of
+   CENSUS_LOG_MAX_RECORD_SIZE (no per-block fragmentation). */
+void test_fill_log_no_fragmentation(void) {
+  const int circular = 0;
+  printf("Starting test: fill log no fragmentation\n");
+  setup_test(circular);
+  fill_log(LOG_SIZE_IN_BYTES, 1 /* no fragmentation */, circular);
+  census_log_shutdown();
+}
+
+/* Fills circular log with records sized such that size is a multiple of
+   CENSUS_LOG_MAX_RECORD_SIZE (no per-block fragmentation). */
+void test_fill_circular_log_no_fragmentation(void) {
+  const int circular = 1;
+  printf("Starting test: fill circular log no fragmentation\n");
+  setup_test(circular);
+  fill_log(LOG_SIZE_IN_BYTES, 1 /* no fragmentation */, circular);
+  census_log_shutdown();
+}
+
+/* Fills non-circular log with records that may straddle end of a block. */
+void test_fill_log_with_straddling_records(void) {
+  const int circular = 0;
+  printf("Starting test: fill log with straddling records\n");
+  setup_test(circular);
+  fill_log(LOG_SIZE_IN_BYTES, 0 /* block straddling records */, circular);
+  census_log_shutdown();
+}
+
+/* Fills circular log with records that may straddle end of a block. */
+void test_fill_circular_log_with_straddling_records(void) {
+  const int circular = 1;
+  printf("Starting test: fill circular log with straddling records\n");
+  setup_test(circular);
+  fill_log(LOG_SIZE_IN_BYTES, 0 /* block straddling records */, circular);
+  census_log_shutdown();
+}
+
+/* Tests scenario where multiple writers and a single reader are using a log
+   that is configured to discard old records. */
+void test_multiple_writers_circular_log(void) {
+  const int circular = 1;
+  printf("Starting test: multiple writers circular log\n");
+  setup_test(circular);
+  multiple_writers_single_reader(circular);
+  census_log_shutdown();
+}
+
+/* Tests scenario where multiple writers and a single reader are using a log
+   that is configured to discard old records. */
+void test_multiple_writers(void) {
+  const int circular = 0;
+  printf("Starting test: multiple writers\n");
+  setup_test(circular);
+  multiple_writers_single_reader(circular);
+  census_log_shutdown();
+}
+
+/* Repeat the straddling records and multiple writers tests with a small log. */
+void test_small_log(void) {
+  size_t log_size;
+  const int circular = 0;
+  printf("Starting test: small log\n");
+  census_log_initialize(0, circular);
+  log_size = census_log_remaining_space();
+  GPR_ASSERT(log_size > 0);
+  fill_log(log_size, 0, circular);
+  census_log_shutdown();
+  census_log_initialize(0, circular);
+  multiple_writers_single_reader(circular);
+  census_log_shutdown();
+}
+
+void test_performance(void) {
+  int write_size = 1;
+  for (; write_size < CENSUS_LOG_MAX_RECORD_SIZE; write_size *= 2) {
+    gpr_timespec write_time;
+    gpr_timespec start_time;
+    double write_time_micro = 0.0;
+    int nrecords = 0;
+    setup_test(0);
+    start_time = gpr_now(GPR_CLOCK_REALTIME);
+    while (1) {
+      void *record = census_log_start_write(write_size);
+      if (record == NULL) {
+        break;
+      }
+      census_log_end_write(record, write_size);
+      nrecords++;
+    }
+    write_time = gpr_time_sub(gpr_now(GPR_CLOCK_REALTIME), start_time);
+    write_time_micro = write_time.tv_sec * 1000000 + write_time.tv_nsec / 1000;
+    census_log_shutdown();
+    printf(
+        "Wrote %d %d byte records in %.3g microseconds: %g records/us "
+        "(%g ns/record), %g gigabytes/s\n",
+        nrecords, write_size, write_time_micro, nrecords / write_time_micro,
+        1000 * write_time_micro / nrecords,
+        (write_size * nrecords) / write_time_micro / 1000);
+  }
+}