How to check Jenkins build executor free memory?

In Jenkins when clicking on Build Executor Status I can only see free disk space related statistics (URI: /computer). How I can monitor free system memory (RAM) in Jenkins?

I'm asking, because sometimes when I had too many executors (despite having swap space configured, but not the one below), Jenkins was freezing or crashing a lot.

Have a look at the Monitoring plugin. Here are some more details about it (from the linked page):

• Charts of memory, cpu, system load average, http response times by day, week, month, year or custom period

• Statistics of http requests with mean response times, mean cpu times, mean response size by request and by day, week, month, year or custom period

• Errors and logs

• Current http requests

• Threads

• Heap histogram (instances and sizes by class)

• Http sessions

• Process list of OS

• MBeans

• Actions for GC, heap dump and invalidate session(s)

• Report in html or pdf

• In English, German, French, Portuguese or Chinese

• Jenkins security

• For Jenkins nodes (slaves in general):

• The report for the nodes is available at http://yourhost/monitoring/nodes

• Charts aggregated for all nodes of memory, cpu, system load average, number of running builds, build queue length, build times by period

• Detailed statistics of the build times and of the build steps by period

• Threads, process list and MBeans for each nodes

• Heap histogram aggregated for all nodes

• For each individual node (each node in http://yourhost/computer), reports and actions are available from the "Monitoring" page in the contextual menu or in the detail of the node:

• Threads, process list, MBeans of that node only

• Heap histogram of that node

• Actions for GC, heap dump

• And more...

Credits: Assaf Lavie (who first mentioned it in a comment, but for some reason didn't post that as an actual answer ...).

StackExchange DevOps Q#173, answer score: 10