Windows standby and sleep

1. Why do we need to wait and sleep?

Although the computer hardware runs faster and faster, the size of the operating system is also expanding, making the computer start, shut downProgramIt takes longer and longer time. Therefore, how to enable the computer to quickly start and access windows as soon as it is started becomes a concern for users.

As a result, with the upgrade of hardware and software, the operating system began to introduce advanced power management, its role is to shut down some devices when the computer is idle, the computer enters the waiting state, in this way, when the computer needs to be re-used, it can be restored directly from waiting for the rest state to the original working state as soon as possible, which is similar to the effect of quick start; at the same time, it can save a lot of energy when the computer is not used.

2. store data in memory-standby

We all know that reading data from a hard disk is much faster than reading data from memory. Therefore, when the computer is running, it first proposes and saves the data in the hard disk to the memory, then the memory sends the data to the CPU for processing, and then the processed data will first return to the memory, then write it into the hard disk. Almost all running data is stored in the memory. However, in the standby mode, the current data is stored in the memory, and the hard disk is closed, that is, suspended to the memory (suspend to ram, STR for short ).

In this case, other devices except the hard disk are still in the power-on wait state (that is to say, do not need to re-power up when waking up, generally speaking, it is on standby ), so the power supply, CPU, graphics card and other equipment fan is still in the work, the keyboard indicator is also on. We can press any key on the keyboard or move the mouse to wake up the computer, then the hard disk will power up and start again, and then exchange data with memory, CPU and other devices, this completes the task returned to the original working status.

3. Load the memory into the hard disk-sleep

Sleep, in a broad sense, includes suspending to memory (STR, that is, standby) and suspending to hard disk (suspend to disk, STD, the sleep we usually refer to is actually STD. When the computer enters sleep state, the computer first copies the state in memory to the hard disk, and then power off. At this time, the computer is almost as quiet as it is usually shut down. You can completely cut off the power, because the data stored in the hard disk will not be lost due to power failure! It is the same as that used by ghost to mirror the system. However, unlike ghost, ghost stores and restores the overall system information, while sleep stores and restores the system running information. Compared with the standby mode, sleep cannot be awakened by an external device. It starts the computer just like normal boot. However, after sleep, the computer does not need to be started one by one, you only need to read the memory image from the hard disk to the memory.

Because the information in the memory is the current "status" of the computer, to keep this state unchanged (it can be understood that it cannot be compressed ), the system must create a space equal to the memory size in the hard disk to ensure that the entire memory can be loaded in the "current state". The name of this space is hiberfil. sys, its volume is generally the size of physical memory (for example, the computer memory is 256 MB, and the size of this file will also be 256 MB), and we call the virtual memory pagefile. the sys principle is the same.