Pass the blob URL for preloads in WasmEMCCBenchmark. #74

kmiller68 · 2025-05-27T16:26:18Z

Right now we pass the original path when loading preloads for WasmEMCCBenchmark. This means we might skip the cache and fetch the content from the network again. We don't want to do this because it means the OS might spin down the CPU, which can punish running faster.

I also moved this logic to the prerunCode rather than adding it to the runnerCode since logically that makes more sense.

Lastly, have the preloads tuples contain the path for cli runs. This means we no longer have to duplicate the preload paths into the benchmark.js file.

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Right now we pass the original path when loading preloads for WasmEMCCBenchmark. This means we might skip the cache and fetch the content from the network again. We don't want to do this because it means the OS might spin down the CPU, which can punish running faster. I also moved this logic to the `prerunCode` rather than adding it to the `runnerCode` since logically that makes more sense. As a drive by change, this patch has the preloads tuples contain the path for cli runs. This means we no longer have to duplicate the preload paths into the benchmark.js file. Additionally, remove a console.log of the test that just finished which broke the dumpJSONResults option for the CLIs.

…ion to get the blob as an array buffer in modern browsers.

… that process I also had to change how 8bitbench loads the rom it's going to use.

kmiller68 · 2025-07-01T16:02:15Z

Ugh, unfortunately now the benchmark jetsams on iOS... I might need to get creative with a solution here...

danleh · 2025-07-02T10:40:46Z

8bitbench/benchmark.js

@@ -34,14 +34,24 @@ function dumpFrame(vec) {

 class Benchmark {
  isInstantiated = false;
+  romBinary;
+
+  async init() {


IIUC, this is essentially shared code with the getBinary function in WasmEMCCBenchmark below, just that there it's only used for initializing the Module["wasmBinary"] = getBinary(...) and here it's for an arbitrary (non-Wasm) file, that happens to be the emulator ROM, right?

Can we unify this, ideally also with the mechansim for preloading blogs of JavaScript line items (ARES-6/Babylon below)?

danleh · 2025-07-02T10:40:50Z

Dart/benchmark.js

-      } catch {
-        this.dart2wasmJsModule = await import("./Dart/build/flute.dart2wasm.mjs");
-      }
+      if (!isInBrowser)


So what happens in !isInBrowser environments, where the previous dynamic import threw an exception? In that case, wouldn't we simply not set this.dart2wasmJsModule and fail later? Or do we assume that we only reach here if isInBrowser == false? In that case, can we instead change this to an explicit assertion, e.g.

console.assert(!isInBrowser, "relative imports should always succeed in browsers, this code is only for shells");

or something.

danleh · 2025-07-02T10:44:53Z

JetStreamDriver.js


-        const promise = Promise.all(filePromises).then((texts) => {
+        if (isInBrowser) {
+            this._resourcesPromise = Promise.resolve();


I haven't fully understood the (somewhat intertwined, complex) preload, resource loading code. At a high-level, why do we just early return here having added anything to this.scripts?

danleh · 2025-07-02T10:50:09Z

JetStreamDriver.js

+            return this._resourcesPromise;
+        }
+
+        const filePromises = this.plan.files.map((file) => fileLoader.load(file));


I don't get this in conjunction with fileLoader._loadInternal: Here, we never reach if isInBrowser, because of the early return above. But in fileLoader._loadInternal (from line 199,

JetStream/JetStreamDriver.js

Lines 199 to 225 in 6947a46

async _loadInternal(url) {

if (!isInBrowser)

return Promise.resolve(readFile(url));

let response;

const tries = 3;

while (tries--) {

let hasError = false;

try {

response = await fetch(url);

} catch (e) {

hasError = true;

}

if (!hasError && response.ok)

break;

if (tries)

continue;

globalThis.allIsGood = false;

throw new Error("Fetch failed");

}

if (url.indexOf(".js") !== -1)

return response.text();

else if (url.indexOf(".wasm") !== -1)

return response.arrayBuffer();

throw new Error("should not be reached!");

}

) we early return just early return if (!isInBrowser) Promise.resolve(readFile(url)). In other words, isn't this whole remaining code of fileLoader superfluous?

danleh · 2025-07-02T10:54:29Z

JetStreamDriver.js

@@ -994,9 +993,16 @@ class Benchmark {
        if (this._resourcesPromise)
            return this._resourcesPromise;

-        const filePromises = !isInBrowser ? this.plan.files.map((file) => fileLoader.load(file)) : [];
+        this.preloads = [];
+        this.blobs = [];


AFAICT, this.blobs is never read, can't this be removed?

danleh · 2025-07-02T11:01:07Z

JetStreamDriver.js

+        }
+
+        const filePromises = this.plan.files.map((file) => fileLoader.load(file));
+        this._resourcesPromise = Promise.all(filePromises).then((texts) => {
            if (isInBrowser)


The if (isInBrowser) return; in lines 1006/1007 is dead code now, because of line 999, right?

danleh · 2025-07-02T11:04:38Z

JetStreamDriver.js

    }

-    // FIXME: Why is this part of the runnerCode and not prerunCode?
+    // This is in runnerCode rather than prerunCode because prerunCode isn't currently structured to be async by default.


What is the difference between prerunCode() and Benchmark.init()? The latter is async / called with await for AsyncBenchmark, see

JetStream/JetStreamDriver.js

Line 1138 in 6947a46

await __benchmark.init();

Could one unify the two, or move this code into async init()?

danleh · 2025-07-02T11:07:23Z

JetStreamDriver.js

-                };
-                xhr.send(null);
+                async function getBinary(key, blobURL) {
+                    const response = await fetch(blobURL);


As I said above, this getBinary function is only used for the Wasm binary of Emscripten benchmarks, but could we use some more general mechanism from the JavaScript line items?

danleh · 2025-07-02T11:08:07Z

JetStreamDriver.js

-        for (let i = 0; i < keys.length; ++i) {
-            str += `loadBlob("${keys[i]}", "${this.plan.preload[keys[i]]}", async () => {\n`;
+        for (let [ preloadKey, blobURLOrPath ] of this.preloads) {
+            if (preloadKey == "wasmBinary") {


Can we get rid of this special casing of just the wasmBinary preloadKey? There are not that many Emscripten workloads, so I'd be happy to just add a line Module["wasmBinary"] = genericPreloadFunc(wasmBinary) to every one of those (for a little less "magic").

danleh

Thanks a lot for starting this, the preload/blob loading code is certainly ripe for a simplification/cleanup! (Unfortunately, I haven't fully understood all parts / why it's so complex, so some clarification questions in the review.)

danleh · 2025-07-02T11:10:59Z

Ugh, unfortunately now the benchmark jetsams on iOS... I might need to get creative with a solution here...

Could you explain what the issue is? (Also TIL a new word "jetsams".)

kmiller68 force-pushed the preload-blobs-wasm branch from a9e68ec to 21aa2dc Compare May 29, 2025 14:02

kmiller68 added 2 commits June 26, 2025 10:54

Move blob fetching to runnerCode since it needs to do an async operat…

0234022

…ion to get the blob as an array buffer in modern browsers.

Fix between benchmark network requests for Dart-flute's JS Module. In…

07c8db1

… that process I also had to change how 8bitbench loads the rom it's going to use.

danleh reviewed Jul 2, 2025

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Pass the blob URL for preloads in WasmEMCCBenchmark. #74

Pass the blob URL for preloads in WasmEMCCBenchmark. #74

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	async _loadInternal(url) {
	if (!isInBrowser)
	return Promise.resolve(readFile(url));

	let response;
	const tries = 3;
	while (tries--) {
	let hasError = false;
	try {
	response = await fetch(url);
	} catch (e) {
	hasError = true;
	}
	if (!hasError && response.ok)
	break;
	if (tries)
	continue;
	globalThis.allIsGood = false;
	throw new Error("Fetch failed");
	}
	if (url.indexOf(".js") !== -1)
	return response.text();
	else if (url.indexOf(".wasm") !== -1)
	return response.arrayBuffer();

	throw new Error("should not be reached!");
	}

Pass the blob URL for preloads in WasmEMCCBenchmark. #74

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