src/vs/workbench/services/extensions/common/extensionHostManager.ts/ExtensionHostManager/_measureUp
class ExtensionHostManager:	private async _measureUp(proxy: IExtensionHostProxy): Promise<number> {
		const SIZE = 10 * 1024 * 1024; // 10MB

		let buff = VSBuffer.alloc(SIZE);
		let value = Math.ceil(Math.random() * 256);
		for (let i = 0; i < buff.byteLength; i++) {
			buff.writeUInt8(i, value);
		}
		const sw = StopWatch.create(true);
		await proxy.test_up(buff);
		sw.stop();
		return ExtensionHostManager._convert(SIZE, sw.elapsed());
	}