Today's article about memory analysis was written by ChatGPT. What do you think?

​In Linux, memory usage analysis is very important to ensure that the system has enough resources to run its processes. There are several tools that can help analyze memory usage in Linux, including top, free, vmstat, and smem.

One of the more detailed memory analysis tools is smem, which can provide information about memory usage per process and per user. Some advantages of using smem include the ability to view the size ratio of a process, the size ratio of shared libraries, and the size ratio of all other mappings.

/proc/meminfo is a file in the Linux operating system that provides information about system memory usage. It contains several fields that provide information about system memory usage, including MemFree, which represents the amount of free memory available for use, and MemAvailable, which represents the amount of memory available for use by the system. To determine the memory availability of a Linux system, it is recommended to look at MemAvailable as it provides a more accurate reflection of the system's memory usage.

In the Linux operating system, the OOM (Out of Memory) Killer is a mechanism that automatically kills processes when the system memory is insufficient. The OOM Killer is triggered when the system's available memory and swap space are exhausted. The OOM Killer then selects which processes to kill based on various factors, including the process's memory usage and the process's priority.

In conclusion, analyzing memory usage in Linux is very important to ensure that the system has enough resources to run its processes. There are several tools available for analyzing memory usage, including top, free, vmstat, and smem. Among them, smem is a more detailed memory analysis tool that provides information about memory usage per process and per user. To determine the memory availability of a Linux system, it is recommended to look at the MemAvailable field in the /proc/meminfo file. OOM Killer is a mechanism in the Linux operating system that automatically kills processes when the system runs out of memory.

It seems that the above text is different from Lao Bai’s previous writing style. It is indeed true. The above text was automatically generated by ChatGPT and was generated based on the conversation between me and ChatGPT about Linux memory analysis. a concluding paragraph. Yesterday afternoon, someone was discussing Linux memory-related issues in a WeChat group. I posted an old article for everyone’s reference. Then I suddenly had the idea to discuss this issue with ChatGPT. During the discussion, I came up with the idea of ​​letting it The idea of ​​​​generating an article to publish, but this article is a bit dry, like an instruction manual, but AI can do this, which is already considered good.

This is also a way for IT personnel to use the AI ​​tool ChatGPT. They can use their existing knowledge to expand and learn a certain aspect of knowledge. The following is the details of this conversation. In fact, the following content also contains some of my views on Linux memory analysis. During the conversation, there were actually times when ChatGPT’s answers were not perfect, but as I marked some of the questions, in the final summary above, ChatGPT’s statement was quite accurate.

It is very convenient to use ChatGPT to learn knowledge, but it should be noted that its answers are not necessarily correct. Yesterday, I discussed ChatGPT with my son. He wanted to try it and asked him a few questions about chemistry. In the face of more professional knowledge, many of ChatGPT's answers had problems. My son corrected its view, and it immediately apologized and gave the correct answer.

The following content is the content of the conversation between me and ChatGPT. It is based on the content of this conversation that it generated the text at the beginning of this article . Friends who are interested in Linux memory analysis can continue reading. The content of the conversation is much richer than that dry text.

If you want to analyze the memory usage of LINUX, what tool is better to use

#A commonly used tool to analyze Linux memory usage is free​ and top.

The

free command displays the system's memory usage, including swap area and physical memory.

The top command provides real-time system process and resource monitoring information, and can also view memory usage.

In addition, there are interactive command line tools such as htop, which are more friendly and easier to use than top.

If you want to analyze in more detail, are there any other tools?

If you want to analyze Linux memory usage in more detail In this case, you can also use the following tools:

1.vmstat: reports virtual memory status.

2.sar: System analysis and reporting tool, which can report memory and swap area usage.

3.smem: A tool to analyze process memory usage.

4.pmap: A tool that reports process memory mapping.

5./proc/meminfo: Reports memory statistics. By reading this file, you can obtain the system's memory usage.

The above tools can all help to understand the memory usage of Linux in more detail. Which tool to choose depends on your specific needs.

Can you talk about smem specifically? What are the advantages of smem analyzing memory? What can be analyzed

smem is a command line tool that is used to analyze the memory usage of a process. It reads the system's memory usage statistics and then generates a report for each process. The report includes the physical memory and shared memory used by the process.

Compared with other memory analysis tools, the advantages of smem are:

1. It analyzes process memory usage, not system memory usage.

2. It reports the amount of memory occupied by each process, including physical memory and shared memory.

3. It can generate detailed memory usage reports for each process, making it easy to compare the memory usage of different processes.

By using smem, you can understand the system memory usage of each process and identify those processes that occupy a large amount of memory. This can help you optimize your system's memory usage and avoid out-of-memory issues.

Can you give an example of smem analysis?

Yes, here is a simple smem analysis example:

1. Install smem​ : Use the following command to install smem: sudo apt-get install smem (assuming you are using an Ubuntu system).

2. Run smem​: Enter the smem command in the terminal to generate a memory usage report:

$ smem
SizeCommand
 ----------------------
 124852 kBgnome-shell
 123996 kBgnome-terminal
 122916 kBXorg
 118636 kBfirefox
 117588 kBnautilus

In the above example, smem generated a memory usage report, which includes The memory usage of each process (in KB) and the corresponding commands are shown.

The above example shows the basic usage of smem. You can also use various options of smem to generate more detailed reports. More details can be obtained with the man smem command.

#What does RSS memory refer to?

RSS (Resident Set Size) memory is a commonly used memory indicator, which indicates the actual physical memory size occupied by the process.

In the Linux system, each process has a virtual memory space, and not all pages in this space are loaded into physical memory. Only the pages that need to be used will be loaded into physical memory. RSS refers to the number of pages occupied by the process in physical memory.

Therefore, RSS memory is an important indicator to measure the memory usage of a process. By comparing the size of RSS memory, we can understand the actual occupation of physical memory by each process.

If the sum of the RSS memory of all processes in the system is calculated, does it mean that all processes occupy the total physical memory of the system?

#Yes, if the sum of the RSS memory of all processes is calculated, it can indeed represent the physical memory occupied by all processes in the entire system.

However, during the calculation process, you also need to pay attention to some other factors, such as the memory occupied by the kernel code and shared libraries. If these factors are not considered, the results obtained may be inaccurate. Therefore, it is recommended to use system monitoring tools, such as top or free, etc., to understand the system memory usage.

#Does the RSS memory include the size of the shared memory occupied by the process?

#Yes, RSS memory includes the size of the shared memory occupied by the process.

Shared memory is a memory sharing mechanism in Linux systems that allows multiple processes to share the same memory space, making memory utilization more efficient. If a process occupies shared memory, its RSS memory will contain the size of this shared memory.

Therefore, by looking at the RSS memory of a process, we can understand its actual usage of physical memory and shared memory.

If the RSS of multiple processes using the same shared memory is accumulated and calculated as the sum of the physical memory occupied by these processes, is this calculation correct?

# is incorrect. This calculation is inaccurate.

If multiple processes share the same shared memory, then this shared memory will only be counted once and will not be accumulated multiple times. Therefore, accumulating the RSS of multiple processes using the same shared memory cannot be counted as the total physical memory usage of these processes.

If you want to accurately understand the system memory usage, it is recommended to use system monitoring tools, such as top or free, etc., for monitoring.

#Does RSS include all the physical memory occupied by a process? If not, what other memory is not included in RSS statistics?

RSS memory includes part of the physical memory occupied by a process, but does not include all.

In addition to physical memory, there are some other memories that are not counted in RSS memory, such as:

1. Cache memory: The system caches some file contents. To speed up file reading, this part of memory is not counted in RSS memory.

2. User stack: Each thread has a user stack, which is used to store the thread's function call stack. This part of the memory is not counted in the RSS memory.

3. Memory mapped file: Some processes can map physical memory through memory mapped files. Physical memory may not be occupied during the running of the process, and this part of memory is not counted in RSS memory.

Therefore, RSS memory only reflects part of the physical memory actually used by a process, and does not fully reflect the physical memory usage of the process.

MemFree and MemAvailable in /proc/meminfo, which indicator can better reflect the memory availability in the Linux system

MemAvailable better reflects the memory availability in the Linux system. MemFree only represents the size of unused physical memory, while MemAvailable includes unused physical memory, cache, and memory that can be paged, which can more accurately reflect the memory usage in the system.

If we want to analyze whether to expand the memory of the system, see which one of MemFree and MemAvailable is more suitable

If you want to determine whether you need to expand the memory of the system, it is not enough to look at MemFree or MemAvailable. Because both indicators only refer to the memory situation in the system, they cannot indicate whether the current system is no longer sufficient. Therefore, if you want to determine whether the system needs to expand memory, you need to comprehensively consider the system's memory usage, including the memory usage frequency and memory usage history, the system's hardware configuration, etc., before making a decision.

In Linux, when will OOM KILLER automatically kill the process

In Linux, when memory is tight, OOM Killer will be triggered and automatically kill a process to release memory. When memory is low, the kernel evaluates all processes in the system and selects one to kill to free up memory. OOM Killer will be triggered when there is insufficient memory or a memory leak occurs in the system.

Can you tell me the specific triggering conditions? For example, how high must the SWAP usage be before it is triggered?

The specific triggering conditions may vary depending on the Linux version and system configuration, but usually OOM Killer will be killed under the following circumstances Trigger:

• #When the usage of physical memory and swap space is very high, and the memory cannot be released by freeing memory or swap space.
• When the physical memory usage is high and the remaining memory is not enough to meet the needs of the system.
• When the system memory is insufficient to meet the memory requirements of any one process.

Regarding the specific trigger threshold, it can generally be adjusted by configuring system parameters. For example, you can set the vm.oom_kill_allocating_task parameter to control it. But usually, the OOM Killer trigger threshold is dynamically adjusted by the kernel based on the current system status and memory requirements.

How does OOM killer choose the process to kill

OOM killer chooses the process to kill It is decided based on a certain evaluation strategy. Common evaluation strategies include:

• The memory usage of the process (physical memory and swap space)
• The OOM score of the process, this score represents the kernel’s response to An estimate of the memory footprint of the process.
• The status of the process. If the process is in the TASK_UNINTERRUPTIBLE state, it may be killed first.
• The OOM score of each process can be adjusted through the /proc//oom_score_adj file.

#Can you help me generate an article about what we discussed today?

When analyzing Linux system memory usage, tools such as top, free, vmstat, and smem are good choices. smem is more suitable for analyzing detailed memory usage. It can analyze the memory usage of processes and users, and display the memory usage of processes in different ways. For example, analyze the physical memory usage (RSS) of the process and the shared memory. usage, and the user's memory usage.

RSS memory refers to the physical memory used by the process, but does not include the shared memory occupied by the process. If multiple processes use the same shared memory, their RSS values ​​will be calculated repeatedly, so not all physical memory will be counted in the RSS.

The MemFree and MemAvailable indicators in /proc/meminfo can both reflect the memory availability in the Linux system, but MemAvailable is more accurate. If you want to determine whether the memory needs to be expanded, you can refer to the value of MemAvailable.

When the Linux system memory usage reaches a certain threshold, OOM Killer will automatically kill the process. However, the specific triggering conditions are not fixed because the Linux kernel has many parameters that can be adjusted. OOM Killer will choose to kill the least important process and evaluate the importance of the process through different algorithms.

Can you be more detailed? It seems that there is something missing about the smem tool and the relationship between RSS and shared memory

Sure, here's a more detailed summary of our conversation today:

In Linux, memory usage analysis is important to ensure the system has sufficient resources to run its processes. There are several tools that can help analyze memory usage in Linux, including top​, free​, vmstat​, and smem.

One of the more detailed memory analysis tools is smem​, which can provide information about memory usage per process and per user. Some of the advantages of using smem include being able to see the proportional size of the process, the proportional size of the shared libraries, and the proportional size of all other mappings.

/proc/meminfo​ is a file in the Linux operating system that provides information about the system's memory usage. It contains several fields that provide information about the system's memory usage, including MemFree​, which represents the amount of free memory available for use, and MemAvailable​, which represents the amount of memory available for use by the system. To determine the memory availability of a Linux system, it is recommended to look at MemAvailable, as it provides a more accurate reflection of the system's memory usage.

In the Linux operating system, the OOM (Out of Memory) Killer is a mechanism that automatically kills processes when the system runs out of memory. The OOM Killer is triggered when the system's free memory and swap space are exhausted. The OOM Killer then selects a process to kill based on various factors, such as the process's memory usage and the priority of the process.

In conclusion, analyzing memory usage in Linux is important to ensure the system has sufficient resources to run its processes. There are several tools available for analyzing memory usage, including top​, free​, vmstat​, and smem​. Of these, smem​ is a more detailed memory analysis tool that provides information about memory usage per process and per user. To determine the memory availability of a Linux system, it is recommended to look at the MemAvailable​ field in the /proc/meminfo file. The OOM Killer is a mechanism in the Linux operating system that automatically kills processes when the system runs out of memory.

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