According to the usage statistics of user application from Microsoft, 60% of the time people spend on the PC is within the web browser. Google Chrome is a cross-platform web browser developed by Google based on Chromium project. According to StatCounter website stats, by January 2022, the market share of Chrome browser is over 63% across all platforms worldwide. 

Hybrid core architecture combining high performance cores and power-efficient cores became more and more popular, especially after Intel launched the Alder Lake CPU product. Performance cores are designed to provide maximum compute performance, while efficient cores are designed for maximum power efficiency. Usually OS schedulers can manage hybrid core scheduling, but they lack details of application behaviors, like critical paths. It’s difficult for OS schedulers to cover all scenarios. 

We come from the Web Optimization team, and focus on power and performance optimization for Web platforms, mainly Chromium, aiming for better user experience on IA. This article introduces our work to utilize hybrid core capability to schedule specific threads/processes’ execution in Chrome browser to efficient cores, which adopts dynamic policies to reduce power consumption on different levels based on device state. All the analysis and tests below are performed on the Chrome OS platform.

On the hybrid core platform, Chrome can schedule threads to efficient cores to save power consumption. However, putting browser threads on efficient cores all the time is impractical since lots of threads may surge and demand higher performance. So we propose a hybrid core scheduling technology in Chrome browser to apply dynamic throttles on specific non-critical threads through scheduling them to efficient cores to execute. The technology is based on Web runtime scenarios, like background/idle/ads/video, as the importance of threads would change in different scenarios. Moreover, device information, like battery/thermal status and hybrid core information, need to be exposed to Chrome. Based on them, hybrid core scheduling would apply different core allocation policies to balance power and performance. Normally we schedule low priority threads to efficient cores. But when the device is in a critical stage like running out of battery, the scheduling policy would be more aggressive to prolong device usage time. The application of scheduling policy relies on the OS support, and we can use thread priority or QoS mechanism according to the customs of the OS. On Chrome OS, currently we change thread priority and its cgroup association. Whole architecture of the proposal is shown in Figure 1.

Figure 1: hybrid core scheduling in Chrome browser

On the hybrid core platform, Chrome can schedule threads to efficient cores to save power consumption. However, putting browser threads on efficient cores all the time is impractical since lots of threads may surge and demand higher performance. So we propose a hybrid core scheduling technology in Chrome browser to apply dynamic throttles on specific non-critical threads through scheduling them to efficient cores to execute. The technology is based on Web runtime scenarios, like background/idle/ads/video, as the importance of threads would change in different scenarios. Moreover, device information, like battery/thermal status and hybrid core information, need to be exposed to Chrome. Based on them, hybrid core scheduling would apply different core allocation policies to balance power and performance. Normally we schedule low priority threads to efficient cores. But when the device is in a critical stage like running out of battery, the scheduling policy would be more aggressive to prolong device usage time. The application of scheduling policy relies on the OS support, and we can use thread priority or QoS mechanism according to the customs of the OS. On Chrome OS, currently we change thread priority and its cgroup association. Whole architecture of the proposal is shown in Figure 1.

The implementation of hybrid core scheduling technology mainly contains three parts, scenario detection, scheduling policy, and OS support work.

First we need to determine the current scenario of a process based on inputs from various browser components. For example, the Chrome render process has a status about background state, which indicates whether the process is foreground or background scenario. For another example, Chrome has an Ad Tagging mechanism to detect ads and the resources they load in the browser. Ad Tagging works by matching resource requests against a filter list to determine if they’re ad requests. An iframe will be marked as an ad iframe if its url matches the filter list, if the tagged script is involved in the creation of the iframe, or if its parent frame is an ad iframe. If all frames are ad frames, the render process would be tagged as an ad process. The browser collects all these inputs and uses a prioritization mechanism to decide the overall mode for the process. Based on the scenario, we adopt an appropriate scheduling policy next.

The scheduling policy varies based on the device status. As shown in Figure 1, the browser will monitor the power status of the device via APIs provided by the OS, including the battery level, charging status and the thermal state. For hybrid core scheduling, two stages are defined below.

The first one is the normal stage, which means the battery level is over 20% or the device is charging, meanwhile the thermal state is normal. In this stage, the users care more about the performance than power consumption, so we only schedule low priority threads/processes to efficient cores, like the background processes or the threads handling low priority tasks such as logging/profiling.

The second one is the critical stage, which means the battery level is very low without charging, or the device is in critical thermal states, or the web developer explicitly wants to enter power saving mode, like using battery-savings meta tag. In this stage, we’re going to apply more aggressive policies to save more power, prolong device usage time or avoid thermal throttling due to high CPU temperature. Under this circumstance, many threads/processes in normal priority will be scheduled to efficient cores as long as they are not involved in UX critical tasks.

There is some work required to be done to make Chrome utilize OS capability. Battery and thermal status are two important factors to UX. Based on them, Chrome could make appropriate policies to balance performance and power consumption. Previously, there was only battery status exposed to Chrome. Our team has landed a thermal status notification feature in Chrome. In the feature, we introduced 4 thermal levels: Nominal, Fair, Serious, and Critical referring to Apple’s Thermal Hinting API. So that Chrome can get the real-time thermal status. With battery level, charging and thermal status reported, Chrome would decide which stage to enter and apply different scheduling policies.

Furthermore, we have built a bridge between Chrome threads and efficient cores on Chrome OS using the existing cgroup mechanism. Background priority threads are placed in a specific cgroup, which has a specified CPU set. On hybrid core platforms, efficient cores are likely to be allocated for the group. So if we want to schedule unimportant threads to efficient cores to execute, we can lower the thread priority and put them in the non-urgent cgroup. The scheduling is dynamic. When the threads become important (e.g. switch to foreground), we would raise the thread priority to normal right away, hence remove from the specific cgroup.

We use the local build Chromium browser to evaluate the power impact of hybrid core scheduling per each scenario, currently focusing on background renderer processes, ads processes, and idle processes (idle is a state defined in the Chrome RAIL model). According to the experiments performed on Alder Lake Chromebook, we observe 4.2% CPU package power reduction for web browsing when scheduling idle processes to efficient cores, and 3.8% CPU package power reduction when dispatching advertisement processes. At the same time, we use a 4-tab browsing workload to test the power impact of placing background processes on efficient cores, and see 0.9% CPU package power reduction. The power saving would be larger when the number of background tabs and page activities increase.

The experiment data shows that we achieve distinct power reduction by utilizing hybrid core capability in Chromium browser to schedule non-UX critical processes/threads to efficient cores in chosen scenarios, which helps extend device battery life.

We will continue to explore more scenarios, which don’t demand high performance, and corresponding processes/threads can be scheduled to efficient cores. Besides, as for some scenarios like ads and idle, running on efficient cores might have performance impact, we are about to conduct performance evaluation soon and adjust the scheduling policy accordingly. Furthermore, we intend to extend our analysis and hybrid core scheduling optimization to Windows and Linux platforms.

If you’ve ever tried to answer an email or surf the Internet from your mobile device in public—or even at the office or your house—chances are you connected to a Wi-Fi hotspot. Not only is this connection highly convenient, you also didn’t have to use your smartphone’s data. Not surprisingly, hotspots are becoming an essential part of public infrastructure—and our Internet experience.

Millions of people every day connect to public hotspots for their data needs. By some estimates, there are almost 200 million hotspots around the world, and there will be one hotspot for every 20 people on earth by 2018. Thanks to our modern always-on digital lifestyle, people expect to be constantly connected, and public Wi-Fi access points are expanding to a global network of hotspots to meet those needs.

Before we dive in to how to connect to a hotspot and related security issues, let’s define what we mean. While some people use the terms “hotspot” and “mobile hotspot” interchangeably, they have distinct meanings.

• Hotspot: A hotspot is a physical location where people can access the Internet, typically using Wi-Fi, via a wireless local area network (WLAN) with a router connected to an Internet service provider. Most people refer to these locations as “Wi-Fi hotspots” or “Wi-Fi connections.” Simply put, hotspots are the physical places where users can wirelessly connect their mobile devices, such as smartphones and tablets, to the Internet.
  A hotspot can be in a private location or a public one, such as in a coffee shop, a hotel, an airport, or even an airplane. While many public hotspots offer free wireless access on an open network, others require payment. Later in the article you’ll learn how to connect a mobile device to a Wi-Fi hotspot.
• Mobile hotspot: A mobile hotspot (sometimes called a portable hotspot) is a hotspot that’s just that—mobile! While a “regular” Wi-Fi hotspot is tied to a physical location, you can create a mobile hotspot by using your smartphone’s data connection to connect your laptop to the Internet. This process is called “tethering.” More on this process later.
  You should also know these terms when you’re talking about Wi-Fi hotspots.
• Access point (wireless access point): A wireless access point (WAP) is a networking device that allows a Wi-Fi compliant device to connect to a wired network. The WAP can either be physically connected to a router or be integrated into the router itself. A WAP is not a hotspot, which is the physical location where Wi-Fi access to a WLAN is available.
• Wi-Fi: Wi-Fi is the technology that allows your smartphone or computer to access the Internet through a wireless connection. It uses radio signals to send and receive data between your enabled device and the WAP.
• SSID: A service set identifier (more commonly known as an SSID) is the unique name of a wireless network. You’ll need to know the name of the wireless network to connect to it. Your computer or smartphone can search for available wireless networks; often people name their network for easy identification—anything from “Bob’s phone” to “hotel guests” to “Get off my LAN.”

Now that you understand some of the terms associated with hotspots, let’s learn how to connect to them.

You probably connect your smartphone or laptop to the Internet via several Wi-Fi hotspots throughout your day, whether you’re at your office, in your home, or at public locations like coffee shops and airports. Using hotspots is an easy way to keep connected to your busy life.

Connecting to a wireless hotspot is a simple process. Let’s use your smartphone as an example. You want to answer an email at the airport while you’re waiting for your flight, and you don’t want to use your data. You can set your smartphone to notify you when it’s in range of a wireless network, or you can find wireless networks through your phone’s settings. The steps you need to follow to connect to the Wi-Fi hotspot will depend on the device—Android*, iPhone*, or another brand—but here is an overview.

1. Click the wireless icon on your device to see the names of nearby wireless networks. Select a wireless network; in some cases, you might also have to click “Connect.”
2. Enter the security key or the password. Most wireless networks are secured and require a password to accept a connection. Some networks are unsecured or open and do not require a password; you should take care when accessing them as they could introduce a security risk.
3. Select the network type (home, work, or public, if you are on a Windows* device). Choosing the network type will establish a security level appropriate for your location. If you select “home” or “work,” your device will be discoverable to other devices. Be sure to select “public” if you are in a public location like a coffee shop, hotel, restaurant, airport, and other similar locations.

Depending on where you are and the types of hotspots near you, you may be on either an open, unsecured wireless network or a paid/commercial wireless network. You may be asked to sign up for an account or use a paid service like Boingo* or iPass*, which offer various Wi-Fi access plans depending on how much time you plan use the Internet.

Let’s say, though, that you can’t find a Wi-Fi hotspot nearby. Read on to learn how you can use your smartphone as a portable hotspot.

If you’re in a location that doesn’t have a hotspot and you want to connect your laptop to the Internet, you can use your phone as a mobile Wi-Fi hotspot through a process called “tethering.” This allows your laptop to access the Internet and share your smartphone’s data connection.

While the set-up steps vary depending on your smartphone and your Internet service provider, you can usually find the instructions in your phone’s Settings or Manage Connections menu. For security, you’ll want to make sure that you use a Wi-Fi password so that nearby Internet users can’t access your phone or laptop. Also, be aware that tethering your laptop to your phone will use your phone’s data allowance; so be sure to keep an eye on your usage to avoid any overage fees.

Now that you’re connected, that’s it, right? Well, not exactly. You should be aware that while using Wi-Fi hotspots is a convenient way to stay connected with work, family, and friends. Hotspot connectivity also presents some security risks.

One of the risks of being connected to the Internet is that the very technologies that help us keep up with our work and personal lives can be vulnerable to hackers and identity thieves.

When looking for a public Wi-Fi hotspot, be sure to connect your smartphone or laptop only to reputable providers—for example, the hotel’s or coffee shop’s wireless network. Be wary about connecting to hotspots that have misspellings such as Bongo instead of Boingo, as hackers sometimes use these seemingly innocent names to lure busy users who aren’t paying close attention.

It’s also possible for hackers to distribute malware (software that can damage or disable your computer) through an unsecured Wi-Fi connection, especially if you are using a file-sharing program over the same network.

If you have security concerns about using a public Wi-Fi hotspot, you could consider creating a virtual private network (VPN), which allows you to use to the Internet through an encrypted connection. While this can deter hackers because your data is encrypted, be aware that it will slow down your Internet access because of the processing power required to encrypt and decrypt your transmitted data.

If you’re interested in using a VPN to safeguard yourself online:

• Invest in a monthly service. This is one of the most commonly used solutions. Make sure to do your research before you buy.
• Consider purchasing a VPN-enabled router. There are several models on the market that make setting up your own VPN easy.

With more than 9 billion Wi-Fi-enabled mobile devices expected to be in use by the end of the year, the importance of hotspots and Wi-Fi in our lives really can’t be overstated.

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