build: adjust max_rss on a per-CI-host basis

This avoids pessimizing concurrency on all machines due to e.g. the macOS
machine having high memory usage across the board due to 16K page size.

.forgejo/workflows/ci.yaml

@@ -5,6 +5,7 @@ on:
   push:
     branches:
       - master
+      - max-rss-tuning
   workflow_dispatch:
 
 concurrency:

build.zig

@@ -459,8 +459,29 @@ pub fn build(b: *std.Build) !void {
         .skip_linux = skip_linux,
         .skip_llvm = skip_llvm,
         .skip_libc = skip_libc,
-        // 3888779264 was observed on an x86_64-linux-gnu host.
+        .max_rss = switch (b.graph.host.result.os.tag) {
-        .max_rss = 4000000000,
+            .freebsd => switch (b.graph.host.result.cpu.arch) {
+                .x86_64 => 1, // TODO
+                else => 0,
+            },
+            .linux => switch (b.graph.host.result.cpu.arch) {
+                .aarch64 => 659809075,
+                .loongarch64 => 598902374,
+                .riscv64 => 1, // TODO
+                .s390x => 580596121,
+                .x86_64 => 3290894745,
+                else => 0,
+            },
+            .macos => switch (b.graph.host.result.cpu.arch) {
+                .aarch64 => 767736217,
+                else => 0,
+            },
+            .windows => switch (b.graph.host.result.cpu.arch) {
+                .x86_64 => 603070054,
+                else => 0,
+            },
+            else => 0,
+        },
     }));
 
     test_modules_step.dependOn(tests.addModuleTests(b, .{
@@ -483,6 +504,29 @@ pub fn build(b: *std.Build) !void {
         .skip_llvm = skip_llvm,
         .skip_libc = true,
         .no_builtin = true,
+        .max_rss = switch (b.graph.host.result.os.tag) {
+            .freebsd => switch (b.graph.host.result.cpu.arch) {
+                .x86_64 => 1, // TODO
+                else => 0,
+            },
+            .linux => switch (b.graph.host.result.cpu.arch) {
+                .aarch64 => 639565414,
+                .loongarch64 => 598884352,
+                .riscv64 => 1, // TODO
+                .s390x => 574166630,
+                .x86_64 => 764861644,
+                else => 0,
+            },
+            .macos => switch (b.graph.host.result.cpu.arch) {
+                .aarch64 => 701413785,
+                else => 0,
+            },
+            .windows => switch (b.graph.host.result.cpu.arch) {
+                .x86_64 => 536414208,
+                else => 0,
+            },
+            else => 0,
+        },
     }));
 
     test_modules_step.dependOn(tests.addModuleTests(b, .{
@@ -505,6 +549,29 @@ pub fn build(b: *std.Build) !void {
         .skip_llvm = skip_llvm,
         .skip_libc = true,
         .no_builtin = true,
+        .max_rss = switch (b.graph.host.result.os.tag) {
+            .freebsd => switch (b.graph.host.result.cpu.arch) {
+                .x86_64 => 1, // TODO
+                else => 0,
+            },
+            .linux => switch (b.graph.host.result.cpu.arch) {
+                .aarch64 => 615302758,
+                .loongarch64 => 598974464,
+                .riscv64 => 1, // TODO
+                .s390x => 395555635,
+                .x86_64 => 528128409,
+                else => 0,
+            },
+            .macos => switch (b.graph.host.result.cpu.arch) {
+                .aarch64 => 451389030,
+                else => 0,
+            },
+            .windows => switch (b.graph.host.result.cpu.arch) {
+                .x86_64 => 317852057,
+                else => 0,
+            },
+            else => 0,
+        },
     }));
 
     test_modules_step.dependOn(tests.addModuleTests(b, .{
@@ -526,8 +593,29 @@ pub fn build(b: *std.Build) !void {
         .skip_linux = skip_linux,
         .skip_llvm = skip_llvm,
         .skip_libc = skip_libc,
-        // I observed a value of 5605064704 on the M2 CI.
+        .max_rss = switch (b.graph.host.result.os.tag) {
-        .max_rss = 6165571174,
+            .freebsd => switch (b.graph.host.result.cpu.arch) {
+                .x86_64 => 1, // TODO
+                else => 0,
+            },
+            .linux => switch (b.graph.host.result.cpu.arch) {
+                .aarch64 => 6732817203,
+                .loongarch64 => 3216349593,
+                .riscv64 => 1, // TODO
+                .s390x => 3652514201,
+                .x86_64 => 5554053120,
+                else => 0,
+            },
+            .macos => switch (b.graph.host.result.cpu.arch) {
+                .aarch64 => 8273795481,
+                else => 0,
+            },
+            .windows => switch (b.graph.host.result.cpu.arch) {
+                .x86_64 => 3750236160,
+                else => 0,
+            },
+            else => 0,
+        },
     }));
 
     const unit_tests_step = b.step("test-unit", "Run the compiler source unit tests");
@@ -721,7 +809,29 @@ fn addCompilerMod(b: *std.Build, options: AddCompilerModOptions) *std.Build.Modu
 fn addCompilerStep(b: *std.Build, options: AddCompilerModOptions) *std.Build.Step.Compile {
     const exe = b.addExecutable(.{
         .name = "zig",
-        .max_rss = 7_800_000_000,
+        .max_rss = switch (b.graph.host.result.os.tag) {
+            .freebsd => switch (b.graph.host.result.cpu.arch) {
+                .x86_64 => 1, // TODO
+                else => 0,
+            },
+            .linux => switch (b.graph.host.result.cpu.arch) {
+                .aarch64 => 6240805683,
+                .loongarch64 => 5024158515,
+                .riscv64 => 1, // TODO
+                .s390x => 4997174476,
+                .x86_64 => 5486090649,
+                else => 0,
+            },
+            .macos => switch (b.graph.host.result.cpu.arch) {
+                .aarch64 => 6639145779,
+                else => 0,
+            },
+            .windows => switch (b.graph.host.result.cpu.arch) {
+                .x86_64 => 5770394009,
+                else => 0,
+            },
+            else => 0,
+        },
         .root_module = addCompilerMod(b, options),
     });
     exe.stack_size = stack_size;