Linux Performance Analysis in 60 Seconds

When you first log into a Linux server to investigate a performance issue, the first minute should be spent running a set of standard tools that give a quick overview of system health.

Overview

Running the ten commands listed below provides a rough picture of processes and resource usage within sixty seconds. The output highlights errors and resource saturation, helping you decide where to focus further investigation.

uptime
dmesg | tail
vmstat 1
mpstat -P ALL 1
pidstat 1
iostat -xz 1
free -m
sar -n DEV 1
sar -n TCP,ETCP 1
top

Some commands require the sysstat package. They support the USE method (Utilization, Saturation, Errors) for pinpointing bottlenecks.

1. uptime

$ uptime
23:51:26 up 21:31,  1 user,  load average: 30.02, 26.43, 19.02

Shows the system’s average load for the past 1, 5, and 15 minutes, indicating how many processes are runnable or waiting for I/O.

2. dmesg | tail

$ dmesg | tail
[1880957.563150] perl invoked oom‑killer: …
[1880957.563400] Out of memory: Kill process 18694 (perl) …
[2320864.954447] TCP: Possible SYN flooding on port 7001. Dropping request.

Displays the most recent kernel messages, useful for spotting OOM kills or network drops.

3. vmstat 1

$ vmstat 1
procs ---------memory---------- ---swap-- -----io---- -system-- ------cpu-----
 34  0   0 200889792  73708 591828   0   0   0   5   6  10 96  1  3  0  0
 …

Shows per‑second snapshots of processes, memory, swap, I/O, and CPU breakdown. Important columns include r (runnable processes), free (idle memory), si/so (swap activity), and us, sy, id, wa, st (CPU time distribution).

4. mpstat -P ALL 1

$ mpstat -P ALL 1
CPU   %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle
all   98.47 0.00 0.75 0.00 0.00 0.00 0.00 0.00 0.00 0.78
0     96.04 0.00 2.97 …

Prints per‑CPU utilization, helping to detect unbalanced load or single‑threaded bottlenecks.

5. pidstat 1

$ pidstat 1
UID   PID   %usr %system %guest %CPU CPU Command
0     9     0.00 0.94   0.00  0.94 1 rcuos/0
0   4214    5.66 5.66   0.00 11.32 15 mesos‑slave
…

Provides a rolling view of CPU usage per process, similar to top but without screen‑refresh.

6. iostat -xz 1

$ iostat -xz 1
avg‑cpu: %user %nice %system %iowait %steal %idle
73.96   0.00   3.73   0.03   0.06   22.21
Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq‑sz avgqu‑sz await r_await w_await svctm %util
xvda   0.00   0.23 0.21 0.18 4.52 2.08 …

Shows block‑device statistics; key fields are r/s, w/s, rkB/s, wkB/s (throughput), await (average I/O latency), avgqu‑sz (queue length), and %util (device utilization).

7. free -m

$ free -m
total used free shared buffers cached
Mem: 245998 24545 221453 83 59 541
‑/+ buffers/cache: 23944 222053

Reports memory usage, distinguishing between used memory, buffers, and page cache.

8. sar -n DEV 1

$ sar -n DEV 1
IFACE   rxpck/s txpck/s rxkB/s txkB/s rxcmp/s txcmp/s rxmcst/s %ifutil
eth0   18763.00 5032.00 20686.42 478.30 0.00 0.00 0.00 0.00
…

Monitors network interface throughput and utilization.

9. sar -n TCP,ETCP 1

$ sar -n TCP,ETCP 1
active/s passive/s iseg/s oseg/s
1.00    0.00    10233.00 18846.00
…

Shows TCP statistics such as active/passive connections and retransmissions, useful for detecting network‑related problems.

10. top

$ top
Tasks: 871 total, 1 running, 868 sleeping …
%Cpu(s): 96.8 us, 0.4 sy, 2.7 id, 0.1 wa …
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
20248 root 20 0 0.227t 0.012t 18748 S 3090 5.2 …

Provides a real‑time snapshot of the most active processes and overall system metrics, complementing the earlier per‑second tools.

Together these commands give a rapid, reproducible “first‑60‑seconds” checklist for Linux performance troubleshooting, allowing you to identify saturation, errors, and resource‑heavy processes before diving deeper with more detailed profiling.