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.

1. 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  3176

   The 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.

2. 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  0.0

   RSS is shown in KiB by default. Use it with %MEM to find processes holding physical memory instead of only large virtual address space.

3. 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.py

   args 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.

4. 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.

5. 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 bash

   RES is the resident memory column in top. In interactive top, press M to sort by memory.

6. 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