[build] Enable racing mode for Dart actions.

Put local actions in a common pool, especially
 - Assembler (many run for boringssl)
 - Linker (high memory use)
 - Dart (high memory use)

This should limit the number of concurrent local actions to the number of harts available, avoiding the racing actions triggering out-of-memory failures.

Change-Id: Ifa168012d73472a3db349acc36545dd176385bbc
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/510190
Commit-Queue: Ryan Macnak <rmacnak@google.com>
Reviewed-by: Alexander Aprelev <aam@google.com>

build/dart/dart_action.gni

@@ -44,6 +44,10 @@ _is_dart = _dart_root == get_path_info("//", "abspath")
 
 if (_is_dart) {
   import("../toolchain/rbe.gni")
+  _dart_action_pool = "//build/toolchain:local_action_pool($host_toolchain)"
+} else {
+  _dart_action_pool =
+      "$_dart_root/build/dart:dart_action_pool($default_toolchain)"
 }
 
 template("_compiled_action") {
@@ -100,8 +104,9 @@ template("_compiled_action") {
                 "--exec_strategy=" + rbe_expensive_exec_strategy,
                 "--",
               ]
-    } else if (!defined(invoker.pool)) {
-      pool = "$_dart_root/build/dart:dart_action_pool($default_toolchain)"
+    }
+    if (!defined(invoker.pool)) {
+      pool = _dart_action_pool
     }
 
     args += [ rebase_path(host_executable, root_build_dir) ] + invoker.args
@@ -156,8 +161,9 @@ template("_prebuilt_tool_action") {
                 "--exec_strategy=" + rbe_expensive_exec_strategy,
                 "--",
               ]
-    } else if (!defined(invoker.pool)) {
-      pool = "$_dart_root/build/dart:dart_action_pool($default_toolchain)"
+    }
+    if (!defined(invoker.pool)) {
+      pool = _dart_action_pool
     }
 
     args += [ rebase_path(invoker.binary, root_build_dir) ] + vm_args
@@ -419,6 +425,7 @@ template("dartaotruntime_action") {
                              "deps",
                              "inputs",
                              "metadata",
+                             "mnemonic",
                              "outputs",
                              "pool",
                              "script",

build/toolchain/BUILD.gn

@@ -0,0 +1,12 @@
+# Copyright (c) 2026, the Dart project authors.  Please see the AUTHORS file
+# for details. All rights reserved. Use of this source code is governed by a
+# BSD-style license that can be found in the LICENSE file.
+
+# Define the pool only in one toolchain so all the toolchains share one pool.
+# default_toolchain would make a bit more sense, but it isn't defined yet when
+# the default toolchain is being evaluated.
+if (current_toolchain == host_toolchain) {
+  pool("local_action_pool") {
+    depth = exec_script("../dart/num_cpus.py", [], "value")
+  }
+}

build/toolchain/fuchsia/fuchsia_toolchain.gni

@@ -93,6 +93,7 @@ template("fuchsia_toolchain") {
     }
 
     tool("asm") {
+      pool = "//build/toolchain:local_action_pool($host_toolchain)"
       depfile = "{{output}}.d"
       command = "$asm -MD -MF $depfile $target_triple_flags $sysroot_flags $lto_flags {{defines}} {{include_dirs}} {{asmflags}} {{cflags}} {{cflags_c}} -c {{source}} -o {{output}}"
       depsformat = "gcc"
@@ -102,6 +103,7 @@ template("fuchsia_toolchain") {
     }
 
     tool("alink") {
+      pool = "//build/toolchain:local_action_pool($host_toolchain)"
       rspfile = "{{output}}.rsp"
       command = "rm -f {{output}} && $ar rcs {{output}} @$rspfile"
       description = "AR {{output}}"
@@ -113,6 +115,7 @@ template("fuchsia_toolchain") {
     }
 
     tool("solink") {
+      pool = "//build/toolchain:local_action_pool($host_toolchain)"
       soname = "{{target_output_name}}{{output_extension}}"  # e.g. "libfoo.so".
       sofile = "{{root_out_dir}}/$soname"  # Possibly including toolchain dir.
       unstripped_sofile =
@@ -160,6 +163,7 @@ template("fuchsia_toolchain") {
     }
 
     tool("link") {
+      pool = "//build/toolchain:local_action_pool($host_toolchain)"
       exename = "{{target_output_name}}{{output_extension}}"
       outfile = "{{root_out_dir}}/$exename"
       rspfile = "$outfile.rsp"

build/toolchain/gcc_toolchain.gni

@@ -117,6 +117,8 @@ template("gcc_toolchain") {
     }
 
     tool("asm") {
+      pool = "//build/toolchain:local_action_pool($host_toolchain)"
+
       # For GCC we can just use the C compiler to compile assembly.
       depfile = "{{output}}.d"
       command = "$asm -MMD -MF $depfile {{defines}} {{include_dirs}} {{asmflags}} -c {{source}} -o {{output}}"
@@ -127,6 +129,7 @@ template("gcc_toolchain") {
     }
 
     tool("alink") {
+      pool = "//build/toolchain:local_action_pool($host_toolchain)"
       rspfile = "{{output}}.rsp"
       command = "rm -f {{output}} && $ar rcs {{output}} @$rspfile"
       description = "AR {{output}}"
@@ -138,6 +141,7 @@ template("gcc_toolchain") {
     }
 
     tool("solink") {
+      pool = "//build/toolchain:local_action_pool($host_toolchain)"
       soname = "{{target_output_name}}{{output_extension}}"  # e.g. "libfoo.so".
       sofile = "{{root_out_dir}}/$soname"  # Possibly including toolchain dir.
       rspfile = sofile + ".rsp"
@@ -190,6 +194,7 @@ template("gcc_toolchain") {
     }
 
     tool("link") {
+      pool = "//build/toolchain:local_action_pool($host_toolchain)"
       exename = "{{target_output_name}}{{output_extension}}"
       outfile = "{{root_out_dir}}/$exename"
       rspfile = "$outfile.rsp"

build/toolchain/mac/mac_toolchain.gni

@@ -101,6 +101,7 @@ template("mac_toolchain") {
 
     tool("asm") {
       # For GCC we can just use the C compiler to compile assembly.
+      pool = "//build/toolchain:local_action_pool($host_toolchain)"
       depfile = "{{output}}.d"
       command = "$asm -MMD -MF $depfile {{defines}} {{include_dirs}} $sysroot_flags $toolchain_flags {{asmflags}} -c {{source}} -o {{output}}"
       depsformat = "gcc"
@@ -128,6 +129,7 @@ template("mac_toolchain") {
     }
 
     tool("alink") {
+      pool = "//build/toolchain:local_action_pool($host_toolchain)"
       rspfile = "{{output}}.rsp"
       command = "rm -f {{output}} && $ar rcs {{output}} @$rspfile"
       description = "AR {{output}}"
@@ -139,6 +141,7 @@ template("mac_toolchain") {
     }
 
     tool("solink") {
+      pool = "//build/toolchain:local_action_pool($host_toolchain)"
       dylib = "{{root_out_dir}}/{{target_output_name}}{{output_extension}}"  # eg
                                                                              # "./libfoo.dylib"
       rspfile = dylib + ".rsp"
@@ -203,6 +206,7 @@ template("mac_toolchain") {
     }
 
     tool("link") {
+      pool = "//build/toolchain:local_action_pool($host_toolchain)"
       exename = "{{target_output_name}}{{output_extension}}"
       outfile = "{{root_out_dir}}/$exename"
       rspfile = "$outfile.rsp"

build/toolchain/rbe.gni

@@ -19,10 +19,13 @@ declare_args() {
   # Set to the docker image to use in the RBE.
   rbe_image = "docker://gcr.io/cloud-marketplace/google/debian11@sha256:69e2789c9f3d28c6a0f13b25062c240ee7772be1f5e6d41bb4680b63eae6b304"
 
-  # Do expensive RBE actions remotely, falling back to local on failure/timeout.
-  # The "racing" strategy can cause a memory exhaustion problem if too many
-  # actions run locally at the same time.
-  rbe_expensive_exec_strategy = "remote_local_fallback"
+  # Do expensive RBE actions locally and remotely, taking whichever completes
+  # first. Local machines are generally faster than the RBE workers, so this
+  # usually takes the local action unless there is a cache hit.
+  # Depends on expensive actions also being limited by a GN/Ninja pool to
+  # prevent memory exhaustion from too many steps running locally at the same
+  # time. Migration to SISO would handle this better.
+  rbe_expensive_exec_strategy = "racing"
 
   rbe_exec_root = rebase_path("//", root_build_dir)
 

build/toolchain/win/msvc_toolchain.gni

@@ -113,6 +113,7 @@ template("msvc_toolchain") {
     }
 
     tool("rc") {
+      pool = "//build/toolchain:local_action_pool($host_toolchain)"
       command = "$python_path $tool_wrapper_path rc-wrapper $env rc.exe /nologo {{defines}} {{include_dirs}} /fo{{output}} {{source}}"
       depsformat = "msvc"
       outputs = [
@@ -122,6 +123,7 @@ template("msvc_toolchain") {
     }
 
     tool("asm") {
+      pool = "//build/toolchain:local_action_pool($host_toolchain)"
       if (toolchain_args.current_cpu == "x86") {
         command = "$python_path $tool_wrapper_path asm-wrapper $env ml.exe {{defines}} {{include_dirs}} {{asmflags}} /c /Fo {{output}} {{source}}"
       } else if (toolchain_args.current_cpu == "x64") {
@@ -149,6 +151,7 @@ template("msvc_toolchain") {
     }
 
     tool("alink") {
+      pool = "//build/toolchain:local_action_pool($host_toolchain)"
       rspfile = "{{output}}.rsp"
       command = "$python_path $tool_wrapper_path link-wrapper $env False $lib /nologo /ignore:4221 /OUT:{{output}} @$rspfile"
       description = "LIB {{output}}"
@@ -165,6 +168,7 @@ template("msvc_toolchain") {
     }
 
     tool("solink") {
+      pool = "//build/toolchain:local_action_pool($host_toolchain)"
       dllname = "{{root_out_dir}}/{{target_output_name}}{{output_extension}}"  # e.g.
                                                                                # foo.dll
       libname = "{{root_out_dir}}/{{target_output_name}}{{output_extension}}.lib"  # e.g.
@@ -173,9 +177,10 @@ template("msvc_toolchain") {
 
       link_command = "$python_path $tool_wrapper_path link-wrapper $env False $link /nologo /IMPLIB:$libname /DLL /OUT:$dllname /PDB:${dllname}.pdb @$rspfile"
 
-      # TODO(brettw) support manifests
-      #manifest_command = "$python_path $tool_wrapper_path manifest-wrapper $env mt.exe -nologo -manifest $manifests -out:${dllname}.manifest"
-      #command = "cmd /c $link_command && $manifest_command"
+      # TODO(brettw) support manifests #manifest_command = "$python_path
+      # $tool_wrapper_path manifest-wrapper $env mt.exe -nologo -manifest
+      # $manifests -out:${dllname}.manifest" #command = "cmd /c $link_command &&
+      # $manifest_command"
       command = link_command
 
       default_output_extension = ".dll"
@@ -195,6 +200,7 @@ template("msvc_toolchain") {
     }
 
     tool("solink_module") {
+      pool = "//build/toolchain:local_action_pool($host_toolchain)"
       dllname =
           "{{output_dir}}/{{target_output_name}}{{output_extension}}"  # e.g.
                                                                        # foo.dll
@@ -219,6 +225,7 @@ template("msvc_toolchain") {
     }
 
     tool("link") {
+      pool = "//build/toolchain:local_action_pool($host_toolchain)"
       binary_output =
           "{{root_out_dir}}/{{target_output_name}}{{output_extension}}"
       rspfile = "$binary_output.rsp"
@@ -226,9 +233,10 @@ template("msvc_toolchain") {
 
       link_command = "$python_path $tool_wrapper_path link-wrapper $env False $link /nologo /OUT:$binary_output /PDB:$pdbfile @$rspfile"
 
-      # TODO(brettw) support manifests
-      #manifest_command = "$python_path $tool_wrapper_path manifest-wrapper $env mt.exe -nologo -manifest $manifests -out:{{output}}.manifest"
-      #command = "cmd /c $link_command && $manifest_command"
+      # TODO(brettw) support manifests #manifest_command = "$python_path
+      # $tool_wrapper_path manifest-wrapper $env mt.exe -nologo -manifest
+      # $manifests -out:{{output}}.manifest" #command = "cmd /c $link_command &&
+      # $manifest_command"
       command = link_command
 
       default_output_extension = ".exe"