May 19, 2021 21:00:00

Apple's M1 chip makes users think 'fast' by devising a way to handle tasks

The proprietary SoC 'M1 ' announced by Apple in November 2020 is installed in 'MacBook Air ', ' Mac mini ', ' MacBook Pro ', etc., and has recorded excellent benchmark scores and actually It has also been praised by the media that reviewed it. Regarding such an M1 chip, it is newly pointed out that 'In addition to simply having high performance, the M1 chip maintains user comfort by devising a task processing method.'

How M1 Macs feel faster than Intel models: it's about QoS – The Eclectic Light Company
https://eclecticlight.co/2021/05/17/how-m1-macs-feel-faster-than-intel-models-its-about-qos/

Apple's M1 is a fast CPU—but M1 Macs feel even faster due to QoS | Ars Technica
https://arstechnica.com/gadgets/2021/05/apples-m1-is-a-fast-cpu-but-m1-macs-feel-even-faster-due-to-qos/

When thinking about computer performance, it is common to equate 'throughput, ' which indicates how many tasks can be processed in a given amount of time, with performance. Throughput is easy to measure, and many people think that 'improving throughput will improve performance.'

However, what the actual computer user perceives is not the throughput, but the ' latency ' that is the time from when the task is processed until the response is returned. As a result, even if you maximize throughput at the expense of latency, users will find it 'slow' because the computer is slow to respond.

Howard Oakley, a writer for Mac-related articles, said the M1 chip's simple processing power and devised ways to handle tasks reduce the latency that users feel. The process is fast. ' Mr. Oakley says that the important factor in the processing of the M1 chip is the ' Quality of Service (QoS) ' required by the application.

QoS is a technology that prioritizes important things by prioritizing packets and tasks, and manages the availability of services appropriately. Developers of apps for macOS can assign five QoS levels to their apps, from the lowest priority 'background ' to the highest priority ' userInteractive ', and macOS handles tasks according to these QoS levels. To do.

However, Oakley points out that even with the same macOS, there are differences in the way tasks are handled between Intel processors and M1 chips. When Oakley actually performed the task of compressing a 10GB test file on a macOS device with an Intel processor, the process was performed using all cores at all QoS levels.

On the other hand, when the high-performance core 'Firestorm' and the high-efficiency core 'Icestorm' with low power consumption were tested on the M1 chip consisting of 4 cores each, a total of 8 cores, the QoS level was set to 'background'. If so, the task was executed only on the high efficiency core. In this case, the high performance core was not used for processing even when it was completely in standby. Furthermore, if the QoS level is set higher than 'background', processing is executed in all eight cores including high-performance cores, and processing is completed faster than when processing is performed only in high-efficiency cores. He said he did.

The image below shows the CPU usage when using Time Machine , which is a backup function of macOS. You can see that most of the processing is done on the high efficiency core, and sometimes only a small amount is done on the high performance core.

by Howard Oakley

There are two types of cores in the M1 chip, high efficiency cores exist mainly for macOS and many background tasks, and high performance cores are waiting for users to perform tasks. I will. In other words, since the user task can be processed by the high-performance core even while the background task is being executed, the latency felt by the user is reduced and the user feels 'fast'.

'The slowdown of the interface in the face of OS issues can make a very bad impression on users,' Oakley said. If a Mac with an Intel processor encounters background task issues, it can also adversely affect user processes, but even if a Mac with an M1 chip encounters background task issues, it's high performance. The user process is unaffected because it does not affect the core.

Foreign media Ars Technica said, 'Apple's M1 chip feels very fast not because four cores are slower than the others. It maximizes throughput to reduce task latency. It's an ambitious OS that sacrifices. '