Seize Linux Gold in 60 Seconds
If your Linux server suddenly experiences a load surge and alarm text messages continue to flood into your mobile phone, how can you find the root cause of Linux performance problems in the shortest possible time? You may wish to refer to this blog post from the Netflix Performance Engineering Team to learn how they can quickly diagnose machine performance issues in one minute through ten commands.
Overview
By executing the following command, you can have a general understanding of the system resource usage within 1 minute.
- 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 of these commands require the sysstat package to be installed, and some are provided by the procps package. The output of these commands helps to quickly locate performance bottlenecks and check the utilization, saturation and error metrics of all resources (CPU, memory, disk IO, etc.), which is the so-called USE method.
Let’s introduce these commands one by one. For more parameters and instructions on these commands, please refer to the command manual.
uptime
$ uptime 23:51:26 up 21:31, 1 user, load average: 30.02, 26.43, 19.02
This command can quickly check the load status of the machine. In Linux systems, these data represent the number of processes waiting for CPU resources and blocked in uninterruptible IO processes (process status is D). This data can give us a macro understanding of system resource usage.
The output of thecommand indicates the average load conditions for 1 minute, 5 minutes, and 15 minutes respectively. Through these three data, you can understand whether the server load is becoming tight or easing in the area. If the 1-minute average load is very high and the 15-minute average load is very low, it means that the server is commanding a high load and you need to further investigate where the CPU resources are being consumed. On the other hand, if the 15-minute load average is high and the 1-minute load average is low, it is possible that the time when CPU resources are tight has passed.
The output in the above example shows that the average load in the last minute is very high and much higher than the load in the last 15 minutes. Therefore, we need to continue to investigate which processes in the current system consume a lot of resources. You can further investigate by using vmstat, mpstat and other commands that will be introduced below.
dmesg丨tail
$ dmesg | tail [1880957.563150] perl invoked oom-killer: gfp_mask=0x280da, order=0, oom_score_adj=0 [...] [1880957.563400] Out of memory: Kill process 18694 (perl) score 246 or sacrifice child [1880957.563408] Killed process 18694 (perl) total-vm:1972392kB, anon-rss:1953348kB, file-rss:0kB [2320864.954447] TCP: Possible SYN flooding on port 7001. Dropping request. Check SNMP counters.
This command will output the last 10 lines of the system log. In the output in the example, you can see a kernel oom kill and a TCP packet loss. These logs can help troubleshoot performance issues. Don't forget this step.
vmstat 1
$ vmstat 1 procs ---------memory---------- ---swap-- -----io---- -system-- ------cpu----- r b swpd free buff cache si so bi bo in cs us sy id wa st 34 0 0 200889792 73708 591828 0 0 0 5 6 10 96 1 3 0 0 32 0 0 200889920 73708 591860 0 0 0 592 13284 4282 98 1 1 0 0 32 0 0 200890112 73708 591860 0 0 0 0 9501 2154 99 1 0 0 0 32 0 0 200889568 73712 591856 0 0 0 48 11900 2459 99 0 0 0 0 32 0 0 200890208 73712 591860 0 0 0 0 15898 4840 98 1 1 0 0
vmstat(8) command, each line will output some core system indicators, which allow us to understand the system status in more detail. The following parameter 1 indicates that statistical information is output once per second. The header prompts the meaning of each column. These columns introduce some columns related to performance tuning:
- r: Number of processes waiting for CPU resources. This data reflects the CPU load better than the average load. The data does not include processes waiting for IO. If this value is greater than the number of machine CPU cores, then the machine's CPU resources are saturated.
- free: The amount of available memory in the system (in kilobytes). If the remaining memory is insufficient, it will also cause system performance problems. The free command introduced below can provide a more detailed understanding of system memory usage.
- si, so: The number of writes and reads in the swap area. If this data is not 0, it means that the system is already using the swap area (swap) and the machine's physical memory is insufficient.
- us, sy, id, wa, st: These all represent the consumption of CPU time. They respectively represent user time (user), system (kernel) time (sys), idle time (idle), IO waiting time (wait) and Stolen time (stolen, usually consumed by other virtual machines).
The above CPU times allow us to quickly understand whether the CPU is busy. Generally, if the sum of user time and system time is very large, the CPU is busy executing instructions. If the IO wait time is long, the bottleneck of the system may be disk IO.
示例命令的输出可以看见，大量CPU时间消耗在用户态，也就是用户应用程序消耗了CPU时间。这不一定是性能问题，需要结合r队列，一起分析。
mpstat-P ALL 1
$ mpstat -P ALL 1 Linux 3.13.0-49-generic (titanclusters-xxxxx) 07/14/2015 _x86_64_ (32 CPU) 07:38:49 PM CPU %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle 07:38:50 PM all 98.47 0.00 0.75 0.00 0.00 0.00 0.00 0.00 0.00 0.78 07:38:50 PM 0 96.04 0.00 2.97 0.00 0.00 0.00 0.00 0.00 0.00 0.99 07:38:50 PM 1 97.00 0.00 1.00 0.00 0.00 0.00 0.00 0.00 0.00 2.00 07:38:50 PM 2 98.00 0.00 1.00 0.00 0.00 0.00 0.00 0.00 0.00 1.00 07:38:50 PM 3 96.97 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 3.03 [...]
该命令可以显示每个CPU的占用情况，如果有一个CPU占用率特别高，那么有可能是一个单线程应用程序引起的。
pidstat 1
$ pidstat 1 Linux 3.13.0-49-generic (titanclusters-xxxxx) 07/14/2015 _x86_64_ (32 CPU) 07:41:02 PM UID PID %usr %system %guest %CPU CPU Command 07:41:03 PM 0 9 0.00 0.94 0.00 0.94 1 rcuos/0 07:41:03 PM 0 4214 5.66 5.66 0.00 11.32 15 mesos-slave 07:41:03 PM 0 4354 0.94 0.94 0.00 1.89 8 java 07:41:03 PM 0 6521 1596.23 1.89 0.00 1598.11 27 java 07:41:03 PM 0 6564 1571.70 7.55 0.00 1579.25 28 java 07:41:03 PM 60004 60154 0.94 4.72 0.00 5.66 9 pidstat 07:41:03 PM UID PID %usr %system %guest %CPU CPU Command 07:41:04 PM 0 4214 6.00 2.00 0.00 8.00 15 mesos-slave 07:41:04 PM 0 6521 1590.00 1.00 0.00 1591.00 27 java07:41:04 PM 0 6564 1573.00 10.00 0.00 1583.00 28 java 07:41:04 PM 108 6718 1.00 0.00 0.00 1.00 0 snmp-pass 07:41:04 PM 60004 60154 1.00 4.00 0.00 5.00 9 pidstat
pidstat命令输出进程的CPU占用率，该命令会持续输出，并且不会覆盖之前的数据，可以方便观察系统动态。如上的输出，可以看见两个JAVA进程占用了将近1600%的CPU时间，既消耗了大约16个CPU核心的运算资源。
iostat-xz 1
$ iostat -xz 1 Linux 3.13.0-49-generic (titanclusters-xxxxx) 07/14/2015 _x86_64_ (32 CPU) 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 34.37 0.00 9.98 13.80 5.42 2.44 0.09 xvdb 0.01 0.00 1.02 8.94 127.97 598.53 145.79 0.00 0.43 1.78 0.28 0.25 0.25 xvdc 0.01 0.00 1.02 8.86 127.79 595.94 146.50 0.00 0.45 1.82 0.30 0.27 0.26 dm-0 0.00 0.00 0.69 2.32 10.47 31.69 28.01 0.01 3.23 0.71 3.98 0.13 0.04 dm-1 0.00 0.00 0.00 0.94 0.01 3.78 8.00 0.33 345.84 0.04 346.81 0.01 0.00 dm-2 0.00 0.00 0.09 0.07 1.35 0.36 22.50 0.00 2.55 0.23 5.62 1.78 0.03 [...]
iostat命令主要用于查看机器磁盘IO情况。该命令输出的列，主要含义是：
- r/s, w/s, rkB/s, wkB/s：分别表示每秒读写次数和每秒读写数据量（千字节）。读写量过大，可能会引起性能问题。
- await：IO操作的平均等待时间，单位是毫秒。这是应用程序在和磁盘交互时，需要消耗的时间，包括IO等待和实际操作的耗时。如果这个数值过大，可能是硬件设备遇到了瓶颈或者出现故障。
- avgqu-sz：向设备发出的请求平均数量。如果这个数值大于1，可能是硬件设备已经饱和（部分前端硬件设备支持并行写入）。
- %util：设备利用率。这个数值表示设备的繁忙程度，经验值是如果超过60，可能会影响IO性能（可以参照IO操作平均等待时间）。如果到达100%，说明硬件设备已经饱和。
如果显示的是逻辑设备的数据，那么设备利用率不代表后端实际的硬件设备已经饱和。值得注意的是，即使IO性能不理想，也不一定意味这应用程序性能会不好，可以利用诸如预读取、写缓存等策略提升应用性能。
free -m
$ free -m total used free shared buffers cached Mem: 245998 24545 221453 83 59 541 -/+ buffers/cache: 23944 222053 Swap: 0 0 0
free命令可以查看系统内存的使用情况，-m参数表示按照兆字节展示。最后两列分别表示用于IO缓存的内存数，和用于文件系统页缓存的内存数。需要注意的是，第二行-/+ buffers/cache，看上去缓存占用了大量内存空间。这是Linux系统的内存使用策略，尽可能的利用内存，如果应用程序需要内存，这部分内存会立即被回收并分配给应用程序。因此，这部分内存一般也被当成是可用内存。
如果可用内存非常少，系统可能会动用交换区（如果配置了的话），这样会增加IO开销（可以在iostat命令中提现），降低系统性能。
sar -n DEV 1
$ sar -n DEV 1 Linux 3.13.0-49-generic (titanclusters-xxxxx) 07/14/2015 _x86_64_ (32 CPU) 12:16:48 AM IFACE rxpck/s txpck/s rxkB/s txkB/s rxcmp/s txcmp/s rxmcst/s %ifutil 12:16:49 AM eth0 18763.00 5032.00 20686.42 478.30 0.00 0.00 0.00 0.00 12:16:49 AM lo 14.00 14.00 1.36 1.36 0.00 0.00 0.00 0.00 12:16:49 AM docker0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 12:16:49 AM IFACE rxpck/s txpck/s rxkB/s txkB/s rxcmp/s txcmp/s rxmcst/s %ifutil 12:16:50 AM eth0 19763.00 5101.00 21999.10 482.56 0.00 0.00 0.00 0.00 12:16:50 AM lo 20.00 20.00 3.25 3.25 0.00 0.00 0.00 0.00 12:16:50 AM docker0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sar命令在这里可以查看网络设备的吞吐率。在排查性能问题时，可以通过网络设备的吞吐量，判断网络设备是否已经饱和。如示例输出中，eth0网卡设备，吞吐率大概在22 Mbytes/s，既176 Mbits/sec，没有达到1Gbit/sec的硬件上限。
sar -n TCP,ETCP 1
$ sar -n TCP,ETCP 1 Linux 3.13.0-49-generic (titanclusters-xxxxx) 07/14/2015 _x86_64_ (32 CPU) 12:17:19 AM active/s passive/s iseg/s oseg/s 12:17:20 AM 1.00 0.00 10233.00 18846.00 12:17:19 AM atmptf/s estres/s retrans/s isegerr/s orsts/s 12:17:20 AM 0.00 0.00 0.00 0.00 0.00 12:17:20 AM active/s passive/s iseg/s oseg/s 12:17:21 AM 1.00 0.00 8359.00 6039.00 12:17:20 AM atmptf/s estres/s retrans/s isegerr/s orsts/s 12:17:21 AM 0.00 0.00 0.00 0.00 0.00
sar命令在这里用于查看TCP连接状态，其中包括：
- active/s：每秒本地发起的TCP连接数，既通过connect调用创建的TCP连接；
- passive/s：每秒远程发起的TCP连接数，即通过accept调用创建的TCP连接；
- retrans/s：每秒TCP重传数量；
TCP连接数可以用来判断性能问题是否由于建立了过多的连接，进一步可以判断是主动发起的连接，还是被动接受的连接。TCP重传可能是因为网络环境恶劣，或者服务器压力过大导致丢包。
top
$ top top - 00:15:40 up 21:56, 1 user, load average: 31.09, 29.87, 29.92 Tasks: 871 total, 1 running, 868 sleeping, 0 stopped, 2 zombie %Cpu(s): 96.8 us, 0.4 sy, 0.0 ni, 2.7 id, 0.1 wa, 0.0 hi, 0.0 si, 0.0 st KiB Mem: 25190241+total, 24921688 used, 22698073+free, 60448 buffers KiB Swap: 0 total, 0 used, 0 free. 554208 cached Mem 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 29812:58 java 4213 root 20 0 2722544 64640 44232 S 23.5 0.0 233:35.37 mesos-slave 66128 titancl+ 20 0 24344 2332 1172 R 1.0 0.0 0:00.07 top 5235 root 20 0 38.227g 547004 49996 S 0.7 0.2 2:02.74 java 4299 root 20 0 20.015g 2.682g 16836 S 0.3 1.1 33:14.42 java 1 root 20 0 33620 2920 1496 S 0.0 0.0 0:03.82 init 2 root 20 0 0 0 0 S 0.0 0.0 0:00.02 kthreadd 3 root 20 0 0 0 0 S 0.0 0.0 0:05.35 ksoftirqd/0 5 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kworker/0:0H 6 root 20 0 0 0 0 S 0.0 0.0 0:06.94 kworker/u256:0 8 root 20 0 0 0 0 S 0.0 0.0 2:38.05 rcu_sched
top命令包含了前面好几个命令的检查的内容。比如系统负载情况（uptime）、系统内存使用情况（free）、系统CPU使用情况（vmstat）等。因此通过这个命令，可以相对全面的查看系统负载的来源。同时，top命令支持排序，可以按照不同的列排序，方便查找出诸如内存占用最多的进程、CPU占用率最高的进程等。
但是，top命令相对于前面一些命令，输出是一个瞬间值，如果不持续盯着，可能会错过一些线索。这时可能需要暂停top命令刷新，来记录和比对数据。
总 结
排查Linux服务器性能问题还有很多工具，上面介绍的一些命令，可以帮助我们快速的定位问题。例如前面的示例输出，多个证据证明有JAVA进程占用了大量CPU资源，之后的性能调优就可以针对应用程序进行。
The above is the detailed content of Seize Linux Gold in 60 Seconds. For more information, please follow other related articles on the PHP Chinese website!
What are the main tasks of a Linux system administrator?Apr 19, 2025 am 12:23 AMThe main tasks of Linux system administrators include system monitoring and performance tuning, user management, software package management, security management and backup, troubleshooting and resolution, performance optimization and best practices. 1. Use top, htop and other tools to monitor system performance and tune it. 2. Manage user accounts and permissions through useradd commands and other commands. 3. Use apt and yum to manage software packages to ensure system updates and security. 4. Configure a firewall, monitor logs, and perform data backup to ensure system security. 5. Troubleshoot and resolve through log analysis and tool use. 6. Optimize kernel parameters and application configuration, and follow best practices to improve system performance and stability.
Is it hard to learn Linux?Apr 18, 2025 am 12:23 AMLearning Linux is not difficult. 1.Linux is an open source operating system based on Unix and is widely used in servers, embedded systems and personal computers. 2. Understanding file system and permission management is the key. The file system is hierarchical, and permissions include reading, writing and execution. 3. Package management systems such as apt and dnf make software management convenient. 4. Process management is implemented through ps and top commands. 5. Start learning from basic commands such as mkdir, cd, touch and nano, and then try advanced usage such as shell scripts and text processing. 6. Common errors such as permission problems can be solved through sudo and chmod. 7. Performance optimization suggestions include using htop to monitor resources, cleaning unnecessary files, and using sy
What is the salary of Linux administrator?Apr 17, 2025 am 12:24 AMThe average annual salary of Linux administrators is $75,000 to $95,000 in the United States and €40,000 to €60,000 in Europe. To increase salary, you can: 1. Continuously learn new technologies, such as cloud computing and container technology; 2. Accumulate project experience and establish Portfolio; 3. Establish a professional network and expand your network.
What is the main purpose of Linux?Apr 16, 2025 am 12:19 AMThe main uses of Linux include: 1. Server operating system, 2. Embedded system, 3. Desktop operating system, 4. Development and testing environment. Linux excels in these areas, providing stability, security and efficient development tools.
Does the internet run on Linux?Apr 14, 2025 am 12:03 AMThe Internet does not rely on a single operating system, but Linux plays an important role in it. Linux is widely used in servers and network devices and is popular for its stability, security and scalability.
What are Linux operations?Apr 13, 2025 am 12:20 AMThe core of the Linux operating system is its command line interface, which can perform various operations through the command line. 1. File and directory operations use ls, cd, mkdir, rm and other commands to manage files and directories. 2. User and permission management ensures system security and resource allocation through useradd, passwd, chmod and other commands. 3. Process management uses ps, kill and other commands to monitor and control system processes. 4. Network operations include ping, ifconfig, ssh and other commands to configure and manage network connections. 5. System monitoring and maintenance use commands such as top, df, du to understand the system's operating status and resource usage.
Boost Productivity with Custom Command Shortcuts Using Linux AliasesApr 12, 2025 am 11:43 AMIntroduction Linux is a powerful operating system favored by developers, system administrators, and power users due to its flexibility and efficiency. However, frequently using long and complex commands can be tedious and er
What is Linux actually good for?Apr 12, 2025 am 12:20 AMLinux is suitable for servers, development environments, and embedded systems. 1. As a server operating system, Linux is stable and efficient, and is often used to deploy high-concurrency applications. 2. As a development environment, Linux provides efficient command line tools and package management systems to improve development efficiency. 3. In embedded systems, Linux is lightweight and customizable, suitable for environments with limited resources.
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
DVWA
Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software
VSCode Windows 64-bit Download
A free and powerful IDE editor launched by Microsoft
SublimeText3 Mac version
God-level code editing software (SublimeText3)
SAP NetWeaver Server Adapter for Eclipse
Integrate Eclipse with SAP NetWeaver application server.
Dreamweaver Mac version
Visual web development tools
