[build] Increase link parallelism again

Budget fewer CPU resources for link actions since lld generally can't sustain
the full level of parallelism requested for long in practice.
This is also helpful since the tag is also applied when compiling the main C++
file of the given test, which shouldn't need more than one CPU – unfortunately
we can't set that directly.

Author: fhanau

build/kj_test.bzl

@@ -26,8 +26,8 @@ def kj_test(
         ] + deps,
         linkstatic = CC_TEST_LINKSTATIC,
         data = data,
-        # Tag with cpu:4 since this target depends on linkopts_default.
-        tags = tags + ["cpu:4"],
+        # Tag with cpu:2 since this target depends on linkopts_default.
+        tags = tags + ["cpu:2"],
         target_compatible_with = select({
             "@//build/config:no_build": ["@platforms//:incompatible"],
             "//conditions:default": [],

build/wd_cc_benchmark.bzl

@@ -27,8 +27,8 @@ def wd_cc_benchmark(
         ],
         # use the same malloc we use for server
         malloc = "//src/workerd/server:malloc",
-        # Tag with cpu:4 since this target depends on linkopts_default.
-        tags = ["workerd-benchmark", "google_benchmark", "cpu:4"] + tags,
+        # Tag with cpu:2 since this target depends on linkopts_default.
+        tags = ["workerd-benchmark", "google_benchmark", "cpu:2"] + tags,
         size = "large",
         **kwargs
     )

build/wd_cc_binary.bzl

@@ -18,8 +18,8 @@ def wd_cc_binary(
             "//conditions:default": [],
         }) + target_compatible_with,
         visibility = visibility,
-        # Tag with cpu:8 since this target depends on linkopts_tool.
-        tags = tags + ["cpu:8"],
+        # Tag with cpu:4 since this target depends on linkopts_tool.
+        tags = tags + ["cpu:4"],
         deps = deps + ["//build/deps:linkopts_tool"],
         **kwargs
     )

build/wd_rust_binary.bzl

@@ -127,7 +127,7 @@ def wd_rust_binary(
         experimental_use_cc_common_link = 1,
         proc_macro_deps = proc_macro_deps,
         # linkopts_tool links with full optimization, so it is given more CPUs.
-        tags = tags + ["cpu:8" if tool else "cpu:4"],
+        tags = tags + ["cpu:4" if tool else "cpu:2"],
         target_compatible_with = select({
             "@//build/config:no_build": ["@platforms//:incompatible"],
             "//conditions:default": [],
@@ -169,6 +169,6 @@ def wd_rust_binary(
         experimental_use_cc_common_link = 1,
         link_deps = ["//build/deps:linkopts_default", "@@//deps:rust_runtime"],
         size = test_size,
-        # Tag with cpu:4 since this target depends on linkopts_default.
-        tags = ["no-coverage", "cpu:4"],
+        # Tag with cpu:2 since this target depends on linkopts_default.
+        tags = ["no-coverage", "cpu:2"],
     )

build/wd_rust_proc_macro.bzl

@@ -46,8 +46,8 @@ def wd_rust_proc_macro(
             "RUST_TEST_THREADS": "1",
         } | test_env,
         experimental_use_cc_common_link = 1,
-        # Tag with cpu:4 since this target depends on linkopts_default.
-        tags = test_tags + ["no-coverage", "cpu:4"],
+        # Tag with cpu:2 since this target depends on linkopts_default.
+        tags = test_tags + ["no-coverage", "cpu:2"],
         deps = test_deps,
         link_deps = ["@@//deps:rust_runtime", "//build/deps:linkopts_default"],
         target_compatible_with = select({

build/wd_rust_test.bzl

@@ -23,7 +23,7 @@ def wd_rust_test(
         ],
         malloc = "//src/workerd/server:malloc",
         # linkopts_default limits linker parallelism to avoid resource exhaustion.
-        tags = tags + ["no-coverage", "cpu:4"],
+        tags = tags + ["no-coverage", "cpu:2"],
         target_compatible_with = select({
             "@//build/config:no_build": ["@platforms//:incompatible"],
             "//conditions:default": [],