![]() ![]() The memory manager uses an algorithm to determine when idle resident set pages can be added to a free list to be reclaimed for other processes. ![]() As a process continues to execute, the memory manager dynamically updates the resident set to page fault in new data as required and to identify existing resident pages that have not been recently used in the working set. The total memory page faulted in for a process is called its RESIDENT SET, and the WORKING SET for a process is the set of those pages actively in use. If a process is swapped in and out of memory frequently, this can lead to thrashing, where disk I/O can severely degrade performance. Technically, swapping refers to paging all the memory for a process out to disk, but the term is often used synonymously with paging inactive memory out to the swapfile. ![]() The shared page is copied and assigned to the modifying process. Minor page faults share memory pages between multiple processes – no additional data needs to be read from disk to memory.Ī copy-on-write occurs for a shared memory page when one of the processes sharing it needs to modify that page. However, a major page fault can also be the result of reading memory pages that have been written out to the swap file, which could indicate a memory shortage.Ī minor page fault occurs when a process needs data that is in memory and is assigned to another process. Major page faults are expected when a process starts or needs to read in additional data and in these cases do not indicate a problem condition. The Linux memory manager uses the following mechanisms to handle memory for processes:Ī major page fault occurs when a process needs to read in data from disk to memory pages. Memory pages are usually 4 KB, but you can use getconf PAGESIZE to find the default page size on your system. Pages are added and removed dynamically to accommodate memory needed for process execution and data input. When a process is started on Linux, it is assigned memory pages to hold executable code and data read in from disk. In this post we will outline Linux memory management for processes and look at commands to monitor memory usage. Buffer and cache data can be dropped without needing to be swapped out to disk, so the actual memory available for processes includes the buffer/cache memory pages. On Windows, 95% used memory means that 95% of your memory is assigned to processes, and allocating memory for a new process will slow down performance as memory is swapped out to disk to free up enough memory for the new process.įor Linux, memory that is listed as “used” is made up of a combination of memory assigned to processes and memory used by the operating system for caching data and buffering operations. Monitoring memory on Linux can be counter-intuitive if you’re accustomed to monitoring Windows. ![]()
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