iotune: ignore shards with id above max_iodepth

If max_iodepth is less than smp::count, then the
calculated io_depth_per_shard can be zero for shards
with id that is greater or equal to the max_iodepth.
This causes runtime error during random read and
random write measurements.

Such sitation was encountered when iotune was run on
a machine with 128 CPUs and non-RAID disk that showed
max_iodepth=127.

This change introudces a logic that prints a warning in
such case and skips performing measurements on shards
that would have io_depth_per_shard=0.

Refs: #2169

Signed-off-by: Patryk Wrobel <[email protected]>

Closes #2201

apps/iotune/iotune.cc

@@ -563,13 +563,23 @@ class iotune_multi_shard_context {
 
  future<io_rates> write_random_data(size_t buffer_size, std::chrono::duration<double> duration) {
  return _iotune_test_file.map_reduce0([buffer_size, this, duration] (test_file& tf) {
- return tf.write_workload(buffer_size, test_file::pattern::random, per_shard_io_depth(), duration, sharded_rates.local());
+ const auto shard_io_depth = per_shard_io_depth();
+ if (shard_io_depth == 0) {
+ return make_ready_future<io_rates>();
+ } else {
+ return tf.write_workload(buffer_size, test_file::pattern::random, shard_io_depth, duration, sharded_rates.local());
+ }
  }, io_rates(), std::plus<io_rates>());
  }
 
  future<io_rates> read_random_data(size_t buffer_size, std::chrono::duration<double> duration) {
  return _iotune_test_file.map_reduce0([buffer_size, this, duration] (test_file& tf) {
- return tf.read_workload(buffer_size, test_file::pattern::random, per_shard_io_depth(), duration, sharded_rates.local());
+ const auto shard_io_depth = per_shard_io_depth();
+ if (shard_io_depth == 0) {
+ return make_ready_future<io_rates>();
+ } else {
+ return tf.read_workload(buffer_size, test_file::pattern::random, shard_io_depth, duration, sharded_rates.local());
+ }
  }, io_rates(), std::plus<io_rates>());
  }
 
@@ -774,6 +784,12 @@ int main(int ac, char** av) {
  iotune_logger.info("Disk parameters: max_iodepth={} disks_per_array={} minimum_io_size={}",
  test_directory.max_iodepth(), test_directory.disks_per_array(), test_directory.minimum_io_size());
 
+ if (test_directory.max_iodepth() < smp::count) {
+ iotune_logger.warn("smp::count={} is greater than max_iodepth={} - shards above max_io_depth "
+ "will be ignored during random read and random write measurements",
+ smp::count, test_directory.max_iodepth());
+ }
+
  ::iotune_multi_shard_context iotune_tests(test_directory);
  iotune_tests.start().get();
  auto stop = defer([&iotune_tests] () noexcept {