Oracle Linux 7: Identifying Processes Consuming Large Amounts of Buffer/Cache Memory
In a recent update to a software server, the system started experiencing issues a few days later, with the software crashing due to an inability to allocate memory. Upon investigation, it was discovered that certain processes were consuming large amounts of buffer/cache memory. This article will cover the key concepts related to this issue and provide a detailed guide on how to identify such processes in Oracle Linux 7.
Understanding Buffer/Cache Memory
Buffer and cache memory are two types of memory that are used by the Linux kernel to improve system performance. Buffer memory is used to temporarily store data that is being read from or written to a disk, while cache memory is used to store frequently accessed data in memory, reducing the need to access the disk.
Buffer and cache memory are combined and reported as a single value in the memory usage statistics. However, it is important to note that this memory is not "locked" and can be freed by the kernel if other processes require it.
Identifying Processes Consuming Large Amounts of Memory
To identify processes consuming large amounts of buffer/cache memory, you can use the ps command with the -o option to specify the memory usage columns to display. The following command will display the process ID (PID), user, memory usage in kilobytes (RSS), and the percentage of memory used by each process:
ps -eo pid,user,%mem,rss | sort -k3 -nr | head -10This command will display the top 10 processes consuming the most memory. You can modify the number of processes displayed by changing the value passed to the head command.
Identifying Processes Consuming Large Amounts of Buffer/Cache Memory
To identify processes consuming large amounts of buffer/cache memory specifically, you can use the smem command. This command provides a more detailed breakdown of memory usage, including buffer and cache memory. The following command will display the top 10 processes consuming the most buffer/cache memory:
smem -t -k -w -P | sort -k12 -n -r | head -10This command will display the top 10 processes consuming the most buffer/cache memory. The -t option displays the total memory usage, the -k option displays the memory usage in kilobytes, the -w option displays the output in a wide format, and the -P option displays the process name instead of the command line.
Identifying processes consuming large amounts of buffer/cache memory in Oracle Linux 7 can help you diagnose and resolve issues with software crashes due to memory allocation. By using the ps and smem commands, you can quickly identify the top processes consuming the most memory and take action to optimize or terminate them as necessary.