Merge pull request #1796 from github/henrymercer/scaling-ram-larger-r…

…unners-only

Scale the amount of reserved RAM on large runners only

src/util.test.ts

@@ -19,28 +19,79 @@ test("getToolNames", (t) => {
   t.deepEqual(toolNames, ["CodeQL command-line toolchain", "ESLint"]);
 });
 
-test("getMemoryFlag() should return the correct --ram flag", async (t) => {
-  const totalMem = os.totalmem() / (1024 * 1024);
-  const fixedAmount = process.platform === "win32" ? 1536 : 1024;
-  const scaledAmount = 0.02 * totalMem;
-  const expectedMemoryValue = Math.floor(totalMem - fixedAmount);
-  const expectedMemoryValueWithScaling = Math.floor(
-    totalMem - fixedAmount - scaledAmount
+const GET_MEMORY_FLAG_TESTS = [
+  {
+    input: undefined,
+    totalMemoryMb: 8 * 1024,
+    platform: "linux",
+    expectedMemoryValue: 7 * 1024,
+    expectedMemoryValueWithScaling: 7 * 1024,
+  },
+  {
+    input: undefined,
+    totalMemoryMb: 8 * 1024,
+    platform: "win32",
+    expectedMemoryValue: 6.5 * 1024,
+    expectedMemoryValueWithScaling: 6.5 * 1024,
+  },
+  {
+    input: "",
+    totalMemoryMb: 8 * 1024,
+    platform: "linux",
+    expectedMemoryValue: 7 * 1024,
+    expectedMemoryValueWithScaling: 7 * 1024,
+  },
+  {
+    input: "512",
+    totalMemoryMb: 8 * 1024,
+    platform: "linux",
+    expectedMemoryValue: 512,
+    expectedMemoryValueWithScaling: 512,
+  },
+  {
+    input: undefined,
+    totalMemoryMb: 64 * 1024,
+    platform: "linux",
+    expectedMemoryValue: 63 * 1024,
+    expectedMemoryValueWithScaling: 63078, // Math.floor(1024 * (64 - 1 - 0.025 * (64 - 8)))
+  },
+  {
+    input: undefined,
+    totalMemoryMb: 64 * 1024,
+    platform: "win32",
+    expectedMemoryValue: 62.5 * 1024,
+    expectedMemoryValueWithScaling: 62566, // Math.floor(1024 * (64 - 1.5 - 0.025 * (64 - 8)))
+  },
+];
+
+for (const {
+  input,
+  totalMemoryMb,
+  platform,
+  expectedMemoryValue,
+  expectedMemoryValueWithScaling,
+} of GET_MEMORY_FLAG_TESTS) {
+  test(
+    `Memory flag value is ${expectedMemoryValue} without scaling and ${expectedMemoryValueWithScaling} with scaling ` +
+      `for ${
+        input ?? "no user input"
+      } on ${platform} with ${totalMemoryMb} MB total system RAM`,
+    async (t) => {
+      for (const withScaling of [true, false]) {
+        const flag = util.getMemoryFlagValueForPlatform(
+          input,
+          totalMemoryMb * 1024 * 1024,
+          platform,
+          withScaling
+        );
+        t.deepEqual(
+          flag,
+          withScaling ? expectedMemoryValueWithScaling : expectedMemoryValue
+        );
+      }
+    }
   );
-
-  const tests: Array<[string | undefined, boolean, string]> = [
-    [undefined, false, `--ram=${expectedMemoryValue}`],
-    ["", false, `--ram=${expectedMemoryValue}`],
-    ["512", false, "--ram=512"],
-    [undefined, true, `--ram=${expectedMemoryValueWithScaling}`],
-    ["", true, `--ram=${expectedMemoryValueWithScaling}`],
-  ];
-
-  for (const [input, withScaling, expectedFlag] of tests) {
-    const flag = util.getMemoryFlag(input, withScaling);
-    t.deepEqual(flag, expectedFlag);
-  }
-});
+}
 
 test("getMemoryFlag() throws if the ram input is < 0 or NaN", async (t) => {
   for (const input of ["-1", "hello!"]) {

src/util.ts

@@ -153,15 +153,16 @@ export async function withTmpDir<T>(
  */
 function getSystemReservedMemoryMegaBytes(
   totalMemoryMegaBytes: number,
+  platform: string,
   isScalingReservedRamEnabled: boolean
 ): number {
   // Windows needs more memory for OS processes.
-  const fixedAmount = 1024 * (process.platform === "win32" ? 1.5 : 1);
+  const fixedAmount = 1024 * (platform === "win32" ? 1.5 : 1);
 
   if (isScalingReservedRamEnabled) {
-    // Reserve an additional 2% of the total memory, since the amount used by
+    // Reserve an additional 2.5% of the amount of memory above 8 GB, since the amount used by
     // the kernel for page tables scales with the size of physical memory.
-    const scaledAmount = 0.02 * totalMemoryMegaBytes;
+    const scaledAmount = 0.025 * Math.max(totalMemoryMegaBytes - 8 * 1024, 0);
     return fixedAmount + scaledAmount;
   } else {
     return fixedAmount;
@@ -175,8 +176,10 @@ function getSystemReservedMemoryMegaBytes(
  *
  * @returns {number} the amount of RAM to use, in megabytes
  */
-export function getMemoryFlagValue(
+export function getMemoryFlagValueForPlatform(
   userInput: string | undefined,
+  totalMemoryBytes: number,
+  platform: string,
   isScalingReservedRamEnabled: boolean
 ): number {
   let memoryToUseMegaBytes: number;
@@ -186,17 +189,36 @@ export function getMemoryFlagValue(
       throw new Error(`Invalid RAM setting "${userInput}", specified.`);
     }
   } else {
-    const totalMemoryBytes = os.totalmem();
     const totalMemoryMegaBytes = totalMemoryBytes / (1024 * 1024);
     const reservedMemoryMegaBytes = getSystemReservedMemoryMegaBytes(
       totalMemoryMegaBytes,
+      platform,
       isScalingReservedRamEnabled
     );
     memoryToUseMegaBytes = totalMemoryMegaBytes - reservedMemoryMegaBytes;
   }
   return Math.floor(memoryToUseMegaBytes);
 }
 
+/**
+ * Get the value of the codeql `--ram` flag as configured by the `ram` input.
+ * If no value was specified, the total available memory will be used minus a
+ * threshold reserved for the OS.
+ *
+ * @returns {number} the amount of RAM to use, in megabytes
+ */
+export function getMemoryFlagValue(
+  userInput: string | undefined,
+  isScalingReservedRamEnabled: boolean
+): number {
+  return getMemoryFlagValueForPlatform(
+    userInput,
+    os.totalmem(),
+    process.platform,
+    isScalingReservedRamEnabled
+  );
+}
+
 /**
  * Get the codeql `--ram` flag as configured by the `ram` input. If no value was
  * specified, the total available memory will be used minus a threshold