Latency is the time it takes for a system to send a request and get a response back. It measures the delay between when something starts and when it finishes, like the wait time when clicking a link and seeing the page load. Latency shows how quickly a system reacts to an action or how fast data moves from one place to another.

People often notice latency in everyday technology, such as when a video buffers or a game lags. It matters because lower latency means faster responses and a smoother experience. Networks, computers, and servers all have latency that affects how well they work together.

Understanding latency helps explain why some systems feel slow while others run smoothly. It plays a key role in many areas like gaming, video calls, and web browsing, making it important to know what it is and why it matters.

Defining System Latency

System latency is about the delay that happens when data or commands move through a system. It involves how long it takes for an action to start and finish. Different types of latency affect systems in various ways, and it’s important to distinguish latency from other related measures like response time.

What is Latency?

Latency is the time delay between when a request is made and when the system starts responding. This delay is usually measured in milliseconds or even nanoseconds for very fast systems. It shows how quickly a system processes operations or transfers data. For example, when a user clicks a button, latency is the wait time before the action appears on the screen.

Latency matters in networks, computers, and other systems because too much delay causes slow or lagging performance. Lower latency means faster and smoother experiences, especially when many operations need quick processing.

Types of Latency in Systems

There are several common types of latency in systems, each affecting performance differently:

• Network latency: The delay in sending data from one device to another. It depends on distance and network speed.
• Processing latency: The time a system takes to handle an operation or process data internally.
• Disk latency: The delay when reading or writing data to storage devices like hard drives or SSDs.

Each latency type adds to the total delay users experience. Reducing any of these helps improve the system’s speed and efficiency.

Latency vs Response Time

Latency and response time are related but not the same. Latency is the delay before a system starts to act on a request. Response time is the total time from the request to the completion of the entire process.

For example, if a system has 10 milliseconds latency but takes 50 milliseconds to finish an operation, the response time is 50 milliseconds. Response time includes latency plus any additional time needed to complete tasks. Understanding both helps engineers improve system performance effectively.

Factors Affecting Latency

Several specific factors influence how long it takes for data to travel through a system. These include physical distance, traffic on the network, the power of hardware components, and how tasks are managed internally. Each affects latency in unique ways.

Distance and Data Transfer

The physical distance between devices has a direct effect on latency. Signals take time to travel, even at the speed of light. When data moves across countries or continents, delay increases.

Data transfer speed also matters. Larger amounts of data take more time to send and receive. If the connection is slow or unstable, latency grows. Sometimes, a message must cross multiple network points, each adding extra delay.

Together, distance and how fast data moves set a basic limit on how low latency can get in any system.

Network Congestion and ISP Impact

When many users share the same network path, congestion happens. This traffic jam forces data to wait before moving forward, increasing latency.

Internet service providers (ISPs) control the routes data takes. If an ISP has poor routing or limited capacity, delays grow. Congestion can also occur at key nodes or servers that process many requests.

Congestion’s impact varies by time and location. Peak hours usually see higher delay because more devices are online. Managing congestion helps keep latency low and stable.

Hardware and Processor Influence

The hardware inside a device plays a big role in latency. Faster processors complete tasks more quickly, reducing delay before sending data forward.

Storage devices affect latency too. For example, older hard drives take longer to read or write information than modern solid-state drives.

Hardware interrupts, which pause a processor to handle important tasks, can add small delays. Systems with better design minimize these pauses. Overall, stronger hardware leads to faster system response.

Role of Scheduler and Buffer

Schedulers manage the order of tasks inside a system. If a scheduler is slow or inefficient, it delays processing, raising latency.

Buffers temporarily hold data before processing or sending it out. This helps smooth out traffic, but if buffers fill up, they can create a backlog. Too much buffering increases wait time.

A well-tuned scheduler and right-sized buffers help reduce delays. They ensure data flows steadily without unnecessary waiting. This management is important in systems handling many tasks at once.

Optimizing for Low Latency

Latency affects how fast systems respond and perform. Reducing latency involves clear steps like improving hardware, network speed, and software efficiency. But it also has challenges, especially when aiming for ultra-low latency that requires balancing performance with cost and complexity.

Why Low Latency Matters

Low latency means faster response times, which is important in many areas. For example, online gaming, live streaming, and financial trading all need near-instant reactions. If latency is high, users face delays, lag, or slow data updates.

Systems with low latency can handle more real-time data, improving user experience and efficiency. It also helps companies meet strict performance goals in their services and applications. In short, low latency supports smooth and reliable interactions.

Strategies to Reduce Latency

There are different ways to reduce latency depending on the system. Common strategies include:

• Optimizing input/output operations for quick data handling
• Using faster networks or reducing network hops
• Employing protocols like HTTP/2 to allow multiple parallel data streams
• Turning on GPU low-latency modes like NVIDIA Reflex for graphics
• Using cached data to avoid repeated database calls

Often, combining these methods leads to better overall performance.

Challenges with High and Ultra-Low Latency

Achieving ultra-low latency is hard and may increase system complexity. High latency can be caused by slow network connections, overloaded servers, or inefficient software.

Trying to push latency lower can require expensive hardware or major redesigns. In some cases, slight latency improvements might not justify the cost or effort. Balancing low latency while keeping the system stable and scalable is a continuous challenge for engineers.