[Autotuner] Log autotuner config in readable json format. When debugging the autotuner we often want to know the values of the AutotuneConfig.

PiperOrigin-RevId: 847683182

third_party/xla/xla/backends/autotuner/autotuner.cc

@@ -499,6 +499,7 @@ absl::StatusOr<std::vector<Autotuner::ConfigResult>> Autotuner::ProfileAll(
 
   std::optional<ScopedShapedBuffer> reference_output;
   if (autotune_config_.check_buffers) {
+    VLOG(2) << "Checking buffers";
     reference_output = GetReferenceOutput(candidates, *input_buffers);
     if (!reference_output.has_value()) {
       LOG(WARNING) << "No reference output found even though buffer checking "
@@ -605,6 +606,8 @@ std::optional<ScopedShapedBuffer> Autotuner::GetReferenceOutput(
       continue;
     }
     if (profile_result.value().output_buffer.has_value()) {
+      VLOG(2) << "Found reference output for config: "
+              << candidate.config.ToString();
       return std::move(profile_result.value().output_buffer.value());
     }
   }
@@ -732,4 +735,28 @@ std::string Autotuner::Config::ToString() const {
                          UnpackedAnyShortDebugString(*backend_config));
 }
 
+std::string AutotuneConfig::ToString() const {
+  return absl::StrFormat(
+      "{\n"
+      "  \"check_buffers\": %s,\n"
+      "  \"relative_tolerance\": %f,\n"
+      "  \"crash_on_check_failure\": %s,\n"
+      "  \"optimize_scratch_bytes\": %s,\n"
+      "  \"scratch_bytes_window_size_us\": %d,\n"
+      "  \"expect_all_instructions_in_cache\": %s,\n"
+      "  \"dump_logs_to\": \"%s\",\n"
+      "  \"exclude_cublas_config\": %s,\n"
+      "  \"select_first_config\": %s,\n"
+      "  \"use_default_config\": %s,\n"
+      "  \"dump_hlos\": %s\n"
+      "}",
+      check_buffers ? "true" : "false", relative_tolerance,
+      crash_on_check_failure ? "true" : "false",
+      optimize_scratch_bytes ? "true" : "false", scratch_bytes_window_size_us,
+      expect_all_instructions_in_cache ? "true" : "false", dump_logs_to,
+      exclude_cublas_config ? "true" : "false",
+      select_first_config ? "true" : "false",
+      use_default_config ? "true" : "false", dump_hlos ? "true" : "false");
+}
+
 }  // namespace xla

third_party/xla/xla/backends/autotuner/autotuner.h

@@ -87,6 +87,8 @@ struct AutotuneConfig {
   // If true, dump the autotuned instructions to the modules's xla_dump_to or
   // to stdout if not set.
   bool dump_hlos = false;
+
+  std::string ToString() const;
 };
 
 class Autotuner {

third_party/xla/xla/backends/autotuner/autotuner_test.cc

@@ -986,5 +986,36 @@ TEST_F(AutotunerTest, DumpHlos) {
           MatchesRegex(".*\\.test_module\\.autotuner_1\\.add\\.before\\.txt")));
 }
 
+TEST(AutotuneConfigTest, ToString) {
+  AutotuneConfig config;
+  config.check_buffers = true;
+  config.relative_tolerance = 1e-4;
+  config.crash_on_check_failure = false;
+  config.optimize_scratch_bytes = true;
+  config.scratch_bytes_window_size_us = 10;
+  config.expect_all_instructions_in_cache = false;
+  config.dump_logs_to = "/tmp/log";
+  config.exclude_cublas_config = true;
+  config.select_first_config = false;
+  config.use_default_config = true;
+  config.dump_hlos = false;
+
+  std::string expected =
+      "{\n"
+      "  \"check_buffers\": true,\n"
+      "  \"relative_tolerance\": 0.000100,\n"
+      "  \"crash_on_check_failure\": false,\n"
+      "  \"optimize_scratch_bytes\": true,\n"
+      "  \"scratch_bytes_window_size_us\": 10,\n"
+      "  \"expect_all_instructions_in_cache\": false,\n"
+      "  \"dump_logs_to\": \"/tmp/log\",\n"
+      "  \"exclude_cublas_config\": true,\n"
+      "  \"select_first_config\": false,\n"
+      "  \"use_default_config\": true,\n"
+      "  \"dump_hlos\": false\n"
+      "}";
+  EXPECT_EQ(config.ToString(), expected);
+}
+
 }  // namespace
 }  // namespace xla

third_party/xla/xla/service/gpu/autotuning/autotuner_pass.cc

@@ -103,6 +103,7 @@ absl::StatusOr<std::unique_ptr<AutotunerPass>> AutotunerPass::Create(
   bool is_deviceless = stream_executor == nullptr;
   AutotuneConfig autotune_config =
       GetAutotuneConfig(debug_options, is_deviceless, optimize_scratch_bytes);
+  VLOG(1) << "Autotune config: " << autotune_config.ToString();
 
   if (!is_deviceless) {
     profiler = GpuProfiler::Create(