How to check process CPU and memory usage in Linux
When a Linux host feels slow, process-level CPU and memory numbers turn a broad performance complaint into a specific PID, command name, and owner. Checking those fields before restarting services or killing tasks helps separate one busy process from host-wide pressure.
ps reads the process table and reports a point-in-time snapshot. Sorting by %CPU highlights work that has consumed CPU during the current accounting window, while sorting by RSS highlights processes holding resident physical memory.
top samples the same kind of process data repeatedly and is better for short spikes that disappear between ps snapshots. Treat %MEM as a share of visible system memory, read RSS or RES for resident memory, and avoid treating a large VIRT value as physical memory use without confirming the resident column.
Steps to check process CPU and memory usage in Linux:
- List processes by current CPU use.
$ ps -eo pid,user,stat,comm,pcpu,pmem,rss --sort=-pcpu PID USER STAT COMMAND %CPU %MEM RSS 2828 root R python3 100 0.0 9352 1 root Ss bash 0.0 0.0 3232 2827 root S python3 0.0 1.5 194336 2830 root R ps 0.0 0.0 3176The first process rows are the highest sampled CPU users in this ps snapshot. The STAT column shows process state, where R is runnable and D usually means uninterruptible I/O wait.
- List processes by resident memory use.
$ ps -eo pid,user,stat,comm,rss,pmem,pcpu --sort=-rss PID USER STAT COMMAND RSS %MEM %CPU 2827 root S python3 194336 1.5 0.0 2828 root R python3 9352 0.0 99.5 1 root Ss bash 3232 0.0 0.0 2831 root R ps 3172 0.0 0.0RSS is shown in KiB by default. Use it with %MEM to find processes holding physical memory instead of only large virtual address space.
- Inspect the full command line for the target PID.
$ ps -p 2827 -o pid,user,stat,etime,pcpu,pmem,rss,args PID USER STAT ELAPSED %CPU %MEM RSS COMMAND 2827 root S 00:02 0.0 1.5 194336 python3 /opt/app/report-worker.pyargs shows the command line that started the process. Confirm the target this way before changing priority, sending a signal, or assigning ownership of the issue.
- Capture a one-time top snapshot sorted by CPU.
$ top -b -n 1 -o %CPU top - 20:55:18 up 1 day, 8:59, 0 users, load average: 0.67, 0.34, 0.34 Tasks: 4 total, 2 running, 2 sleeping, 0 stopped, 0 zombie %Cpu(s): 12.6 us, 0.0 sy, 0.0 ni, 86.2 id, 1.1 wa, 0.0 hi, 0.0 si, 0.0 st MiB Mem : 11948.5 total, 7200.7 free, 1118.0 used, 3877.1 buff/cache MiB Swap: 4096.0 total, 4096.0 free, 0.0 used. 10830.4 avail Mem PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 2828 root 20 0 15704 9352 5244 R 90.9 0.1 0:02.22 python3 1 root 20 0 5744 3232 2964 S 0.0 0.0 0:00.00 bash 2827 root 20 0 200628 194336 5428 S 0.0 1.6 0:00.00 python3 2833 root 20 0 7560 4912 2400 R 0.0 0.0 0:00.00 top-b -n 1 makes top print one batch-mode sample and exit. In interactive top, press P to sort by CPU.
- Capture a one-time top snapshot sorted by memory.
$ top -b -n 1 -o %MEM top - 20:55:18 up 1 day, 8:59, 0 users, load average: 0.67, 0.34, 0.34 Tasks: 4 total, 2 running, 2 sleeping, 0 stopped, 0 zombie %Cpu(s): 12.4 us, 0.0 sy, 0.0 ni, 87.6 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st MiB Mem : 11948.5 total, 7200.7 free, 1118.0 used, 3877.1 buff/cache MiB Swap: 4096.0 total, 4096.0 free, 0.0 used. 10830.4 avail Mem PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 2827 root 20 0 200628 194336 5428 S 0.0 1.6 0:00.00 python3 2828 root 20 0 15704 9352 5244 R 100.0 0.1 0:02.44 python3 2834 root 20 0 7236 4304 2392 R 0.0 0.0 0:00.00 top 1 root 20 0 5744 3232 2964 S 0.0 0.0 0:00.00 bashRES is the resident memory column in top. In interactive top, press M to sort by memory.
- Choose the next check from the confirmed process pattern.
If the same PID stays at the top, inspect the owning service or application logs before taking action. For a non-critical CPU-heavy task, adjust priority before killing it; for a stuck or runaway process, signal only the confirmed target.
Related: How to change process priority in Linux
Related: How to kill a process in Linux