How can I measure the actual memory usage of an application or process?

Question

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How do you measure the memory usage of an application or process in Linux?

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Answer 1

If the process is not using up too much memory (either because you expect this to be the case, or some other command has given this initial indication), and the process can withstand being stopped for a short period of time, you can try to use the gcore command.

gcore 

Check the size of the generated core file to get a good idea how much memory a particular process is using.

This won't work too well if process is using hundreds of megabytes, or gigabytes, as the core generation could take several seconds or minutes to be created depending on I/O performance. During the core creation the process is stopped (or "frozen") to prevent memory changes. So be careful.

Also make sure the mount point where the core is generated has plenty of disk space and that the system will not react negatively to the core file being created in that particular directory.