Simplify GN pools, use in more places (#52721)

This PR changes from using a different GN pool for each non-compiler tool, to using one GN pool for everything.

Additionally, since we are no longer linking remotely in any configuration, this PR uses the pool for linking.

ObjC and impellerc tasks also do not (yet) run on RBE, so they are also now governed by the pool.

Needs flutter/buildroot#856

Author: zanderso

DEPS

@@ -277,7 +277,7 @@ allowed_hosts = [
 ]
 
 deps = {
-  'src': 'https://github.com/flutter/buildroot.git' + '@' + '70a42312a688890eb1435a8c2760f6cbde324531',
+  'src': 'https://github.com/flutter/buildroot.git' + '@' + '7840a4af027fc21161d4ae14a3d4d9c9bab049a2',
 
   'src/flutter/third_party/depot_tools':
   Var('chromium_git') + '/chromium/tools/depot_tools.git' + '@' + '580b4ff3f5cd0dcaa2eacda28cefe0f45320e8f7',

build/dart/BUILD.gn

@@ -7,17 +7,6 @@ import("//flutter/common/config.gni")
 
 import("$dart_src/build/dart/copy_tree.gni")
 
-declare_args() {
-  # Maximum number of Dart processes to run in parallel.
-  #
-  # To avoid out-of-memory errors we explicitly reduce the number of jobs.
-  concurrent_dart_jobs = 1
-}
-
-pool("dart_pool") {
-  depth = concurrent_dart_jobs
-}
-
 if (build_engine_artifacts) {
   if (flutter_prebuilt_dart_sdk) {
     copy_trees("_copy_trees") {

build/dart/rules.gni

@@ -84,7 +84,7 @@ template("flutter_frontend_server") {
                              ],
                              [ "pool" ])
       deps = common_deps
-      pool = "//flutter/build/dart:dart_pool"
+      pool = "//build/toolchain:toolchain_pool"
       script = "//build/gn_run_binary.py"
       inputs = [ invoker.main_dart ]
       outputs = [ invoker.kernel_output ]
@@ -110,7 +110,7 @@ template("flutter_frontend_server") {
                              ],
                              [ "pool" ])
       deps = common_deps
-      pool = "//flutter/build/dart:dart_pool"
+      pool = "//build/toolchain:toolchain_pool"
       script = "$dart_src/pkg/frontend_server/bin/frontend_server_starter.dart"
       inputs = [ invoker.main_dart ]
       outputs = [ invoker.kernel_output ]
@@ -359,7 +359,7 @@ template("application_snapshot") {
       inputs = extra_inputs
       outputs = [ output ]
       depfile = depfile
-      pool = "//flutter/build/dart:dart_pool"
+      pool = "//build/toolchain:toolchain_pool"
 
       ext = ""
       if (is_win) {
@@ -380,7 +380,7 @@ template("application_snapshot") {
                                "visibility",
                              ])
       script = main_dart
-      pool = "//flutter/build/dart:dart_pool"
+      pool = "//build/toolchain:toolchain_pool"
       deps = extra_deps
       inputs = extra_inputs
       outputs = [ output ]

docs/rbe/rbe.md

@@ -151,14 +151,23 @@ RBE builds can be slow for a few different reasons. The most common reason is
 likely to be that the remote caches are cold. When the caches are warm, a
 compile step consists only of downloading the compiled TU from the cache. When
 the caches are cold, the remote workers must run the compilation commands,
-which takes more time.
+which takes more time. If the worker pool is overloaded, compile commands may
+run locally instead, which will also be slower.
 
 RBE builds can also be slow if your network connection is bandwidth constrained.
 Anecdotally, even with a warm cache, I have noticed slow builds from home due
 to RBE saturating my low-tier Comcast Business connection.
 
+For Googlers on a corp macOS device, both RBE and non-RBE builds can be slow
+due to various background and monitoring processes running. See
+[here](https://buganizer.corp.google.com/issues/324404733#comment16) for how
+to disable some of them. You should also disable Spotlight scanning of the
+engine source directory as described
+[here](go/building-chrome-mac#add-the-source-directory-to-the-spotlight-privacy-list).
+
 When RBE builds are slow, non-RBE builds may be faster, especially incremental
-builds.
+builds. You can disable remote builds without invalidating your existing build
+by setting the environment variable `RBE_exec_strategy=local`.
 
 ### Proxy status and debug logs
 

impeller/tools/BUILD.gn

@@ -339,6 +339,7 @@ template("impellerc") {
              ])
 
   _impellerc(target_name) {
+    pool = "//build/toolchain:toolchain_pool"
     shader_bundle = defined(invoker.shader_bundle)
 
     # When single_invocation is true, impellerc will be invoked exactly once. When it's

impeller/tools/impeller.gni

@@ -71,7 +71,7 @@ template("malioc_analyze_shaders") {
                                        ])
 
                 script = "//build/gn_run_malioc.py"
-                pool = "//flutter/impeller/tools:malioc_pool"
+                pool = "//build/toolchain:toolchain_pool"
 
                 # Nest all malioc output under its own subdirectory of root_gen_dir
                 # so that it's easier to diff it against the state before any changes.

impeller/tools/malioc.gni

@@ -232,7 +232,7 @@ compile_platform("strong_platform") {
     "$root_out_dir/flutter_patched_sdk/vm_outline_strong.dill",
   ]
 
-  pool = "//flutter/build/dart:dart_pool"
+  pool = "//build/toolchain:toolchain_pool"
 
   is_runtime_mode_release =
       flutter_runtime_mode == "release" || flutter_runtime_mode == "jit_release"

lib/snapshot/BUILD.gn

@@ -108,7 +108,7 @@ template("dart_snapshot_aot") {
 
     tool = "$dart_src/runtime/bin:gen_snapshot"
 
-    pool = "//flutter/build/dart:dart_pool"
+    pool = "//build/toolchain:toolchain_pool"
 
     inputs = [ invoker.dart_kernel ]
 

testing/testing.gni

@@ -532,7 +532,7 @@ def to_gn_args(args):
   else:
     gn_args['dart_runtime_mode'] = runtime_mode
 
-  gn_args['concurrent_dart_jobs'] = get_concurrent_jobs('1GB', '1GB')
+  gn_args['concurrent_toolchain_jobs'] = get_concurrent_jobs('1GB', '100MB')
 
   # Hardcoding this avoids invoking a relatively expensive python script from
   # GN, but removes the ability to use git-worktrees in the Dart checkout from
@@ -723,7 +723,6 @@ def to_gn_args(args):
     malioc_path = os.environ.get('MALIOC_PATH')
   if malioc_path:
     gn_args['impeller_malioc_path'] = malioc_path
-    gn_args['impeller_concurrent_malioc_jobs'] = get_concurrent_jobs('1GB', '100MB')
 
   if args.use_glfw_swiftshader:
     if get_host_os() == 'mac':