Update threadpool size options, add CMake options

GregoryComer · GregoryComer · commit 01cc300f8dc7 · 2025-09-09T16:03:09.000-07:00
diff --git a/extension/threadpool/CMakeLists.txt b/extension/threadpool/CMakeLists.txt
@@ -20,6 +20,18 @@ if(NOT CMAKE_CXX_STANDARD)
   set(CMAKE_CXX_STANDARD 17)
 endif()
 
+# Threadpool size specifiers. Mutual exclusion is checking in default.cmake.
+set(_threadpool_size_flag)
+if(EXECUTORCH_THREADPOOL_SIZE)
+  set(_threadpool_size_flag
+      "EXECUTORCH_THREADPOOL_SIZE=${EXECUTORCH_THREADPOOL_SIZE}"
+  )
+elseif(EXECUTORCH_THREADPOOL_USE_ALL_LOGICAL_CORES)
+  set(_threadpool_size_flag "EXECUTORCH_THREADPOOL_USE_ALL_LOGICAL_CORES")
+elseif(EXECUTORCH_THREADPOOL_USE_PERFORMANCE_CORES)
+  set(_threadpool_size_flag "EXECUTORCH_THREADPOOL_USE_PERFORMANCE_CORES")
+endif()
+
 add_library(
   extension_threadpool threadpool.cpp threadpool_guard.cpp thread_parallel.cpp
                        cpuinfo_utils.cpp
@@ -36,7 +48,9 @@ target_include_directories(
     $<BUILD_INTERFACE:${EXECUTORCH_ROOT}/backends/xnnpack/third-party/cpuinfo/include>
     $<BUILD_INTERFACE:${EXECUTORCH_ROOT}/backends/xnnpack/third-party/pthreadpool/include>
 )
-target_compile_definitions(extension_threadpool PUBLIC ET_USE_THREADPOOL)
+target_compile_definitions(
+  extension_threadpool PUBLIC ET_USE_THREADPOOL ${threadpool_size_flag}
+)
 target_compile_options(extension_threadpool PUBLIC ${_common_compile_options})
 
 # Install libraries
diff --git a/extension/threadpool/targets.bzl b/extension/threadpool/targets.bzl
@@ -37,7 +37,7 @@ def define_common_targets():
             "-DET_USE_THREADPOOL",
         ] + (
             # Default to perf heuristic (0) in OSS, all cores (-1) otherwise.
-            ["-DEXECUTORCH_THREADPOOL_SIZE=0"] if runtime.is_oss else ["-DEXECUTORCH_THREADPOOL_SIZE=-1"]
+            ["-DEXECUTORCH_THREADPOOL_USE_PERFORMANCE_CORES"] if runtime.is_oss else ["-DEXECUTORCH_THREADPOOL_USE_ALL_LOGICAL_CORES"]
         ),
         visibility = [
             "//executorch/...",
diff --git a/extension/threadpool/threadpool.cpp b/extension/threadpool/threadpool.cpp
@@ -18,6 +18,28 @@
 
 #include <cpuinfo.h>
 
+// At most one mode should be set.
+#if (                                                           \
+    defined(EXECUTORCH_THREADPOOL_SIZE) &&                      \
+        defined(EXECUTORCH_THREADPOOL_USE_ALL_LOGICAL_CORES) || \
+    defined(EXECUTORCH_THREADPOOL_SIZE) &&                      \
+        defined(EXECUTORCH_THREADPOOL_USE_PERFORMANCE_CORES) || \
+    defined(EXECUTORCH_THREADPOOL_USE_ALL_LOGICAL_CORES) &&     \
+        defined(EXECUTORCH_THREADPOOL_USE_PERFORMANCE_CORES))
+#error Multiple \
+            threadpool size specifiers are set.At most one of                \
+                EXECUTORCH_THREADPOOL_SIZE,                                  \
+    EXECUTORCH_THREADPOOL_USE_ALL_LOGICAL_CORES,                             \
+    and EXECUTORCH_THREADPOOL_USE_PERFORMANCE_CORES may be defined.
+#endif
+
+// Default to EXECUTORCH_THREADPOOL_USE_PERFORMANCE_CORES if no mode is set.
+#if !defined(EXECUTORCH_THREADPOOL_SIZE) &&                  \
+    !defined(EXECUTORCH_THREADPOOL_USE_ALL_LOGICAL_CORES) && \
+    !defined(EXECUTORCH_THREADPOOL_USE_PERFORMANCE_CORES)
+#define EXECUTORCH_THREADPOOL_USE_PERFORMANCE_CORES 1
+#endif
+
 namespace executorch::extension::threadpool {
 
 #if !(defined(WIN32))
@@ -105,16 +127,15 @@ ThreadPool* get_threadpool() {
   // Choose the number of threads according to the EXECUTORCH_THREADPOOL_SIZE
   // value. See the description in threadpool.h.
 
-#if defined(EXECUTORCH_THREADPOOL_SIZE) && ((EXECUTORCH_THREADPOOL_SIZE) > 0)
+#ifdef EXECUTORCH_THREADPOOL_SIZE
   // Use an explicit threadpool size.
-  int num_threads = EXECUTORCH_THREADPOOL_SIZE;
-#elif defined(EXECUTORCH_THREADPOOL_SIZE) && \
-    ((EXECUTORCH_THREADPOOL_SIZE) == -1)
+  static int num_threads = EXECUTORCH_THREADPOOL_SIZE;
+#elif defined(EXECUTORCH_THREADPOOL_USE_ALL_LOGICAL_CORES)
   // Use threads=cores.
-  int num_threads = cpuinfo_get_processors_count();
+  static int num_threads = cpuinfo_get_processors_count();
 #else
-  // Use a performance heuristic.
-  int num_threads =
+  // Set threads equal to the number of performance cores.
+  static int num_threads =
       ::executorch::extension::cpuinfo::get_num_performant_cores();
 #endif
 
diff --git a/extension/threadpool/threadpool.h b/extension/threadpool/threadpool.h
@@ -17,29 +17,20 @@
 /*
  * Threadpool Options:
  *
- * Threadpool size has a sizble affect on performance. The following
- * options are exposed to control the threadpool size.
+ * Threadpool size has a sizble affect on performance. By default, the
+ * threadpool will be sized according to the number of performance cores. This
+ * behavior can be overriden with the following build-time options. Note that
+ * these options are mutually exclusive.
  *
- * EXECUTORCH_THREADPOOL_SIZE: int - Set the size of the threadpool,
- * in number of threads.
- *
- *  Special Values:
- *   -  0: Use a perforance heuristic to determine the default size,
- *          based on the active hardware. This is the default mode
- *          for CMake.
- *   - -1: Set the thread count equal to the number of cores on the
- *          active hardware.
- *
- *   Any other positive value will be interpreted as a thread count.
- *   For example, setting EXECUTORCH_THREADPOOL_SIZE=4 will default
- *   the threadpool to use 4 threads.
+ * - EXECUTORCH_THREADPOOL_USE_PERFORMANCE_CORES (flag) - Sizes the threadpool
+ * equal to the number of performance cores on the system. This is the default
+ * behavior.
+ * - EXECUTORCH_THREADPOOL_USE_ALL_LOGICAL_CORES (flag) - Sizes the threadpool
+ * equal to the number of logical cores on system. This is the historical
+ * behavior.
+ * - EXECUTORCH_THREADPOOL_SIZE: int - An explicit number of threads to use.
  */
 
-#ifndef EXECUTORCH_THREADPOOL_SIZE
-// Default to using a runtime heuristic.
-#define EXECUTORCH_THREADPOOL_SIZE 0
-#endif
-
 namespace executorch::extension::threadpool {
 
 class ThreadPool final {
diff --git a/tools/cmake/preset/default.cmake b/tools/cmake/preset/default.cmake
@@ -176,6 +176,49 @@ define_overridable_option(
   ${_default_executorch_build_cpuinfo}
 )
 
+# Threadpool size options. At most one can be specified. Note that the default
+# is managed in threadpool.cpp to allow the user to specify an alternate mode
+# without needing to explicitly set the default to off.
+define_overridable_option(
+  EXECUTORCH_THREADPOOL_SIZE
+  "The number of threads to use for CPU parallel computation." STRING ""
+)
+define_overridable_option(
+  EXECUTORCH_THREADPOOL_USE_PERFORMANCE_CORES
+  "Set the number of threads used for CPU parallel computation equal to the number of performant CPU cores."
+  BOOL
+  OFF
+)
+define_overridable_option(
+  EXECUTORCH_THREADPOOL_USE_ALL_LOGICAL_CORES
+  "Set the number of threads used for CPU parallel computation equal to the number of logical CPU cores."
+  BOOL
+  OFF
+)
+
+check_required_options_on(
+  IF_ON EXECUTORCH_THREADPOOL_SIZE REQUIRES EXECUTORCH_BUILD_PTHREADPOOL
+  EXECUTORCH_BUILD_CPUINFO
+)
+check_required_options_on(
+  IF_ON EXECUTORCH_THREADPOOL_USE_ALL_LOGICAL_CORES REQUIRES
+  EXECUTORCH_BUILD_PTHREADPOOL EXECUTORCH_BUILD_CPUINFO
+)
+check_required_options_on(
+  IF_ON EXECUTORCH_THREADPOOL_USE_ALL_LOGICAL_CORES REQUIRES
+  EXECUTORCH_BUILD_PTHREADPOOL EXECUTORCH_BUILD_CPUINFO
+)
+
+check_conflicting_options_on(
+  IF_ON EXECUTORCH_THREADPOOL_SIZE CONFLICTS_WITH
+  EXECUTORCH_THREADPOOL_USE_PERFORMANCE_CORES
+  EXECUTORCH_THREADPOOL_USE_ALL_LOGICAL_CORES
+)
+check_conflicting_options_on(
+  IF_ON EXECUTORCH_THREADPOOL_USE_PERFORMANCE_CORES CONFLICTS_WITH
+  EXECUTORCH_THREADPOOL_USE_ALL_LOGICAL_CORES
+)
+
 # TODO(jathu): move this to platform specific presets when created
 set(_default_executorch_build_executor_runner ON)
 if(APPLE AND "${SDK_NAME}" STREQUAL "iphoneos")
