Posts Tagged ‘vmstat’
20 Linux System Monitoring Tools Every SysAdmin Should Know
Written by bixuan on 2010年02月8号 – 17:31原文：http://www.cyberciti.biz/tips/top-linux-monitoring-tools.html
by VIVEK GITE
Need to monitor Linux server performance? Try these built-in command and a few add-on tools. Most Linux distributions are equipped with tons of monitoring. These tools provide metrics which can be used to get information about system activities. You can use these tools to find the possible causes of a performance problem. The commands discussed below are some of the most basic commands when it comes to system analysis and debugging server issues such as:
- Finding out bottlenecks.
- Disk (storage) bottlenecks.
- CPU and memory bottlenecks.
- Network bottlenecks.
#1: top - Process Activity Command
The top program provides a dynamic real-time view of a running system i.e. actual process activity. By default, it displays the most CPU-intensive tasks running on the server and updates the list every five seconds.
Fig.01: Linux top command
Commonly Used Hot Keys
The top command provides several useful hot keys:
| Hot Key | Usage |
|---|---|
| t | Displays summary information off and on. |
| m | Displays memory information off and on. |
| A | Sorts the display by top consumers of various system resources. Useful for quick identification of performance-hungry tasks on a system. |
| f | Enters an interactive configuration screen for top. Helpful for setting up top for a specific task. |
| o | Enables you to interactively select the ordering within top. |
| r | Issues renice command. |
| k | Issues kill command. |
| z | Turn on or off color/mono |
=> Related: How do I Find Out Linux CPU Utilization?
#2: vmstat - System Activity, Hardware and System Information
The command vmstat reports information about processes, memory, paging, block IO, traps, and cpu activity.
# vmstat 3
Sample Outputs:
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------ r b swpd free buff cache si so bi bo in cs us sy id wa st 0 0 0 2540988 522188 5130400 0 0 2 32 4 2 4 1 96 0 0 1 0 0 2540988 522188 5130400 0 0 0 720 1199 665 1 0 99 0 0 0 0 0 2540956 522188 5130400 0 0 0 0 1151 1569 4 1 95 0 0 0 0 0 2540956 522188 5130500 0 0 0 6 1117 439 1 0 99 0 0 0 0 0 2540940 522188 5130512 0 0 0 536 1189 932 1 0 98 0 0 0 0 0 2538444 522188 5130588 0 0 0 0 1187 1417 4 1 96 0 0 0 0 0 2490060 522188 5130640 0 0 0 18 1253 1123 5 1 94 0 0
Display Memory Utilization Slabinfo
# vmstat -m
Get Information About Active / Inactive Memory Pages
# vmstat -a
=> Related: How do I find out Linux Resource utilization to detect system bottlenecks?
#3: w - Find Out Who Is Logged on And What They Are Doing
w command displays information about the users currently on the machine, and their processes.
# w username
# w vivek
Sample Outputs:
17:58:47 up 5 days, 20:28, 2 users, load average: 0.36, 0.26, 0.24 USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT root pts/0 10.1.3.145 14:55 5.00s 0.04s 0.02s vim /etc/resolv.conf root pts/1 10.1.3.145 17:43 0.00s 0.03s 0.00s w
#4: uptime - Tell How Long The System Has Been Running
The uptime command can be used to see how long the server has been running. The current time, how long the system has been running, how many users are currently logged on, and the system load averages for the past 1, 5, and 15 minutes.
# uptime
Output:
18:02:41 up 41 days, 23:42, 1 user, load average: 0.00, 0.00, 0.00
1 can be considered as optimal load value. The load can change from system to system. For a single CPU system 1 - 3 and SMP systems 6-10 load value might be acceptable.
#5: ps - Displays The Processes
ps command will report a snapshot of the current processes. To select all processes use the -A or -e option:
# ps -A
Sample Outputs:
PID TTY TIME CMD
1 ? 00:00:02 init
2 ? 00:00:02 migration/0
3 ? 00:00:01 ksoftirqd/0
4 ? 00:00:00 watchdog/0
5 ? 00:00:00 migration/1
6 ? 00:00:15 ksoftirqd/1
....
.....
4881 ? 00:53:28 java
4885 tty1 00:00:00 mingetty
4886 tty2 00:00:00 mingetty
4887 tty3 00:00:00 mingetty
4888 tty4 00:00:00 mingetty
4891 tty5 00:00:00 mingetty
4892 tty6 00:00:00 mingetty
4893 ttyS1 00:00:00 agetty
12853 ? 00:00:00 cifsoplockd
12854 ? 00:00:00 cifsdnotifyd
14231 ? 00:10:34 lighttpd
14232 ? 00:00:00 php-cgi
54981 pts/0 00:00:00 vim
55465 ? 00:00:00 php-cgi
55546 ? 00:00:00 bind9-snmp-stat
55704 pts/1 00:00:00 ps
ps is just like top but provides more information.
Show Long Format Output
# ps -Al
To turn on extra full mode (it will show command line arguments passed to process):
# ps -AlF
To See Threads ( LWP and NLWP)
# ps -AlFH
To See Threads After Processes
# ps -AlLm
Print All Process On The Server
# ps ax
# ps axu
Print A Process Tree
# ps -ejH
# ps axjf
# pstree
Print Security Information
# ps -eo euser,ruser,suser,fuser,f,comm,label
# ps axZ
# ps -eM
See Every Process Running As User Vivek
# ps -U vivek -u vivek u
Set Output In a User-Defined Format
# ps -eo pid,tid,class,rtprio,ni,pri,psr,pcpu,stat,wchan:14,comm
# ps axo stat,euid,ruid,tty,tpgid,sess,pgrp,ppid,pid,pcpu,comm
# ps -eopid,tt,user,fname,tmout,f,wchan
Display Only The Process IDs of Lighttpd
# ps -C lighttpd -o pid=
OR
# pgrep lighttpd
OR
# pgrep -u vivek php-cgi
Display The Name of PID 55977
# ps -p 55977 -o comm=
Find Out The Top 10 Memory Consuming Process
# ps -auxf | sort -nr -k 4 | head -10
Find Out top 10 CPU Consuming Process
# ps -auxf | sort -nr -k 3 | head -10
#6: free - Memory Usage
The command free displays the total amount of free and used physical and swap memory in the system, as well as the buffers used by the kernel.
# free
Sample Output:
total used free shared buffers cached Mem: 12302896 9739664 2563232 0 523124 5154740 -/+ buffers/cache: 4061800 8241096 Swap: 1052248 0 1052248
=> Related: :
- Linux Find Out Virtual Memory PAGESIZE
- Linux Limit CPU Usage Per Process
- How much RAM does my Ubuntu / Fedora Linux desktop PC have?
#7: iostat - Average CPU Load, Disk Activity
The command iostat report Central Processing Unit (CPU) statistics and input/output statistics for devices, partitions and network filesystems (NFS).
# iostat
Sample Outputs:
Linux 2.6.18-128.1.14.el5 (www03.nixcraft.in) 06/26/2009
avg-cpu: %user %nice %system %iowait %steal %idle
3.50 0.09 0.51 0.03 0.00 95.86
Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sda 22.04 31.88 512.03 16193351 260102868
sda1 0.00 0.00 0.00 2166 180
sda2 22.04 31.87 512.03 16189010 260102688
sda3 0.00 0.00 0.00 1615 0
=> Related: : Linux Track NFS Directory / Disk I/O Stats
#8: sar - Collect and Report System Activity
The sar command is used to collect, report, and save system activity information. To see network counter, enter:
# sar -n DEV | more
To display the network counters from the 24th:
# sar -n DEV -f /var/log/sa/sa24 | more
You can also display real time usage using sar:
# sar 4 5
Sample Outputs:
Linux 2.6.18-128.1.14.el5 (www03.nixcraft.in) 06/26/2009 06:45:12 PM CPU %user %nice %system %iowait %steal %idle 06:45:16 PM all 2.00 0.00 0.22 0.00 0.00 97.78 06:45:20 PM all 2.07 0.00 0.38 0.03 0.00 97.52 06:45:24 PM all 0.94 0.00 0.28 0.00 0.00 98.78 06:45:28 PM all 1.56 0.00 0.22 0.00 0.00 98.22 06:45:32 PM all 3.53 0.00 0.25 0.03 0.00 96.19 Average: all 2.02 0.00 0.27 0.01 0.00 97.70
=> Related: : How to collect Linux system utilization data into a file
#9: mpstat - Multiprocessor Usage
The mpstat command displays activities for each available processor, processor 0 being the first one. mpstat -P ALL to display average CPU utilization per processor:
# mpstat -P ALL
Sample Output:
Linux 2.6.18-128.1.14.el5 (www03.nixcraft.in) 06/26/2009 06:48:11 PM CPU %user %nice %sys %iowait %irq %soft %steal %idle intr/s 06:48:11 PM all 3.50 0.09 0.34 0.03 0.01 0.17 0.00 95.86 1218.04 06:48:11 PM 0 3.44 0.08 0.31 0.02 0.00 0.12 0.00 96.04 1000.31 06:48:11 PM 1 3.10 0.08 0.32 0.09 0.02 0.11 0.00 96.28 34.93 06:48:11 PM 2 4.16 0.11 0.36 0.02 0.00 0.11 0.00 95.25 0.00 06:48:11 PM 3 3.77 0.11 0.38 0.03 0.01 0.24 0.00 95.46 44.80 06:48:11 PM 4 2.96 0.07 0.29 0.04 0.02 0.10 0.00 96.52 25.91 06:48:11 PM 5 3.26 0.08 0.28 0.03 0.01 0.10 0.00 96.23 14.98 06:48:11 PM 6 4.00 0.10 0.34 0.01 0.00 0.13 0.00 95.42 3.75 06:48:11 PM 7 3.30 0.11 0.39 0.03 0.01 0.46 0.00 95.69 76.89
=> Related: : Linux display each multiple SMP CPU processors utilization individually.
#10: pmap - Process Memory Usage
The command pmap report memory map of a process. Use this command to find out causes of memory bottlenecks.
# pmap -d PID
To display process memory information for pid # 47394, enter:
# pmap -d 47394
Sample Outputs:
47394: /usr/bin/php-cgi Address Kbytes Mode Offset Device Mapping 0000000000400000 2584 r-x-- 0000000000000000 008:00002 php-cgi 0000000000886000 140 rw--- 0000000000286000 008:00002 php-cgi 00000000008a9000 52 rw--- 00000000008a9000 000:00000 [ anon ] 0000000000aa8000 76 rw--- 00000000002a8000 008:00002 php-cgi 000000000f678000 1980 rw--- 000000000f678000 000:00000 [ anon ] 000000314a600000 112 r-x-- 0000000000000000 008:00002 ld-2.5.so 000000314a81b000 4 r---- 000000000001b000 008:00002 ld-2.5.so 000000314a81c000 4 rw--- 000000000001c000 008:00002 ld-2.5.so 000000314aa00000 1328 r-x-- 0000000000000000 008:00002 libc-2.5.so 000000314ab4c000 2048 ----- 000000000014c000 008:00002 libc-2.5.so ..... ...... .. 00002af8d48fd000 4 rw--- 0000000000006000 008:00002 xsl.so 00002af8d490c000 40 r-x-- 0000000000000000 008:00002 libnss_files-2.5.so 00002af8d4916000 2044 ----- 000000000000a000 008:00002 libnss_files-2.5.so 00002af8d4b15000 4 r---- 0000000000009000 008:00002 libnss_files-2.5.so 00002af8d4b16000 4 rw--- 000000000000a000 008:00002 libnss_files-2.5.so 00002af8d4b17000 768000 rw-s- 0000000000000000 000:00009 zero (deleted) 00007fffc95fe000 84 rw--- 00007ffffffea000 000:00000 [ stack ] ffffffffff600000 8192 ----- 0000000000000000 000:00000 [ anon ] mapped: 933712K writeable/private: 4304K shared: 768000K
The last line is very important:
- mapped: 933712K total amount of memory mapped to files
- writeable/private: 4304K the amount of private address space
- shared: 768000K the amount of address space this process is sharing with others
=> Related: : Linux find the memory used by a program / process using pmap command
#11 and #12: netstat and ss - Network Statistics
The command netstat displays network connections, routing tables, interface statistics, masquerade connections, and multicast memberships. ss command is used to dump socket statistics. It allows showing information similar to netstat. See the following resources about ss and netstat commands:
- ss: Display Linux TCP / UDP Network and Socket Information
- Get Detailed Information About Particular IP address Connections Using netstat Command
#13: iptraf - Real-time Network Statistics
The iptraf command is interactive colorful IP LAN monitor. It is an ncurses-based IP LAN monitor that generates various network statistics including TCP info, UDP counts, ICMP and OSPF information, Ethernet load info, node stats, IP checksum errors, and others. It can provide the following info in easy to read format:
- Network traffic statistics by TCP connection
- IP traffic statistics by network interface
- Network traffic statistics by protocol
- Network traffic statistics by TCP/UDP port and by packet size
- Network traffic statistics by Layer2 address
Fig.02: General interface statistics: IP traffic statistics by network interface
Fig.03 Network traffic statistics by TCP connection
#14: tcpdump - Detailed Network Traffic Analysis
The tcpdump is simple command that dump traffic on a network. However, you need good understanding of TCP/IP protocol to utilize this tool. For.e.g to display traffic info about DNS, enter:
# tcpdump -i eth1 'udp port 53'
To display all IPv4 HTTP packets to and from port 80, i.e. print only packets that contain data, not, for example, SYN and FIN packets and ACK-only packets, enter:
# tcpdump 'tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)’
To display all FTP session to 202.54.1.5, enter:
# tcpdump -i eth1 'dst 202.54.1.5 and (port 21 or 20'
To display all HTTP session to 192.168.1.5:
# tcpdump -ni eth0 'dst 192.168.1.5 and tcp and port http'
Use wireshark to view detailed information about files, enter:
# tcpdump -n -i eth1 -s 0 -w output.txt src or dst port 80
#15: strace - System Calls
Trace system calls and signals. This is useful for debugging webserver and other server problems. See how to use to trace the process and see What it is doing.
#16: /Proc file system - Various Kernel Statistics
/proc file system provides detailed information about various hardware devices and other Linux kernel information. See Linux kernel /proc documentations for further details. Common /proc examples:
# cat /proc/cpuinfo
# cat /proc/meminfo
# cat /proc/zoneinfo
# cat /proc/mounts
17#: Nagios - Server And Network Monitoring
Nagios is a popular open source computer system and network monitoring application software. You can easily monitor all your hosts, network equipment and services. It can send alert when things go wrong and again when they get better. FAN is “Fully Automated Nagios”. FAN goals are to provide a Nagios installation including most tools provided by the Nagios Community. FAN provides a CDRom image in the standard ISO format, making it easy to easilly install a Nagios server. Added to this, a wide bunch of tools are including to the distribution, in order to improve the user experience around Nagios.
18#: Cacti - Web-based Monitoring Tool
Cacti is a complete network graphing solution designed to harness the power of RRDTool’s data storage and graphing functionality. Cacti provides a fast poller, advanced graph templating, multiple data acquisition methods, and user management features out of the box. All of this is wrapped in an intuitive, easy to use interface that makes sense for LAN-sized installations up to complex networks with hundreds of devices. It can provide data about network, CPU, memory, logged in users, Apache, DNS servers and much more. See how to install and configure Cacti network graphing tool under CentOS / RHEL.
#19: KDE System Guard - Real-time Systems Reporting and Graphing
KSysguard is a network enabled task and system monitor application for KDE desktop. This tool can be run over ssh session. It provides lots of features such as a client/server architecture that enables monitoring of local and remote hosts. The graphical front end uses so-called sensors to retrieve the information it displays. A sensor can return simple values or more complex information like tables. For each type of information, one or more displays are provided. Displays are organized in worksheets that can be saved and loaded independently from each other. So, KSysguard is not only a simple task manager but also a very powerful tool to control large server farms.
Fig.05 KDE System Guard {Image credit: Wikipedia}
See the KSysguard handbook for detailed usage.
#20: Gnome System Monitor - Real-time Systems Reporting and Graphing
The System Monitor application enables you to display basic system information and monitor system processes, usage of system resources, and file systems. You can also use System Monitor to modify the behavior of your system. Although not as powerful as the KDE System Guard, it provides the basic information which may be useful for new users:
- Displays various basic information about the computer’s hardware and software.
- Linux Kernel version
- GNOME version
- Hardware
- Installed memory
- Processors and speeds
- System Status
- Currently available disk space
- Processes
- Memory and swap space
- Network usage
- File Systems
- Lists all mounted filesystems along with basic information about each.
Fig.06 The Gnome System Monitor application
Bounce: Additional Tools
A few more tools:
- nmap - scan your server for open ports.
- lsof - list open files, network connections and much more.
- ntop web based tool - ntop is the best tool to see network usage in a way similar to what top command does for processes i.e. it is network traffic monitoring software. You can see network status, protocol wise distribution of traffic for UDP, TCP, DNS, HTTP and other protocols.
- Conky - Another good monitoring tool for the X Window System. It is highly configurable and is able to monitor many system variables including the status of the CPU, memory, swap space, disk storage, temperatures, processes, network interfaces, battery power, system messages, e-mail inboxes etc.
- GKrellM - It can be used to monitor the status of CPUs, main memory, hard disks, network interfaces, local and remote mailboxes, and many other things.
- vnstat - vnStat is a console-based network traffic monitor. It keeps a log of hourly, daily and monthly network traffic for the selected interface(s).
- htop - htop is an enhanced version of top, the interactive process viewer, which can display the list of processes in a tree form.
- mtr - mtr combines the functionality of the traceroute and ping programs in a single network diagnostic tool.
Did I miss something? Please add your favorite system motoring tool in the comments.
Tags: catcti, free, gnome, htop, iptraf, kde, linux, monitor, mtr, netstat, pmap, sar, ss, strace, sysadmin, tcpdump, tool, top, vmstat, vnstat
Posted in 运维小技巧 | 2 Comments »
Linux System and Performance Monitoring(CPU篇)
Written by bixuan on 2009年08月13号 – 09:41Linux System and Performance Monitoring(CPU篇)
Date: 2009.07.21
Author: Darren Hoch
译: Tonnyom[AT]hotmail.com 2009.08.10
前言: 网上其实有很多关于这方面的文章,那为什么还会有此篇呢,有这么几个原因,是我翻译的动力,第一,概念和内容虽然老套,但都讲得很透彻,而且还很全面.第二,理论结合实际,其中案例分析都不错.第三,不花哨,采用的工具及命令都是最基本的,有助于实际操作.但本人才疏学浅,译文大多数都是立足于自己对原文的理解,大家也可以自己去OSCAN上找原文,如果有什么较大出入,还望留言回复,甚是感激!
1.0 性能监控介绍
性能优化就是找到系统处理中的瓶颈以及去除这些的过程,多数管理员相信看一些相关的”cook book”就可以实现性能优化,通常通过对内核的一些配置是可以简单的解决问题,但并不适合每个环境,性能优化其实是对OS 各子系统达到一种平衡的定义,这些子系统包括了:
CPU
Memory
IO
Network
这些子系统之间关系是相互彼此依赖的,任何一个高负载都会导致其他子系统出现问题.比如:
大量的页调入请求导致内存队列的拥塞
网卡的大吞吐量可能导致更多的 CPU开销
大量的CPU开销又会尝试更多的内存使用请求
大量来自内存的磁盘写请求可能导致更多的 CPU 以及 IO问题
所以要对一个系统进行优化,查找瓶颈来自哪个方面是关键,虽然看似是某一个子系统出现问题,其实有可能是别的子系统导致的.
1.1 确定应用类型
基于需要理解该从什么地方来入手优化瓶颈,首先重要的一点,就是理解并分析当前系统的特点,多数系统所跑的应用类型,主要为2种:
IO Bound(译注:IO 范畴): 在这个范畴中的应用,一般都是高负荷的内存使用以及存储系统,这实际上表示IO 范畴的应用,就是一个大量数据处理的过程.IO 范畴的应用不对CPU以及网络发起更多请求(除非类似NAS这样的网络存储硬件).IO 范畴的应用通常使用CPU 资源都是为了产生IO 请求以及进入到内核调度的sleep 状态.通常数据库软件(译注:mysql,oracle等)被认为是IO 范畴的应用类型.
CPU Bound(译注:CPU 范畴): 在这个范畴中的应用,一般都是高负荷的CPU 占用. CPU 范畴的应用,就是一个批量处理CPU 请求以及数学计算的过程.通常web server,mail server,以及其他类型服务被认为是CPU 范畴的应用类型.
1.2 确定基准线统计
系统利用率情况,一般随管理员经验以及系统本身用途来决定.唯一要清楚的就是,系统优化希望达成什么效果,以及哪些方面是需要优化,还有参考值是什么?因此就建立一个基准线,这个统计数据必须是系统可用性能状态值,用来比较不可用性能状态值.
在以下例子中,1个系统性能的基准线快照,用来比较当高负荷时的系统性能快照.
# vmstat 1
procs memory swap io system cpu
r b swpd free buff cache si so bi bo in cs us sy wa id
1 0 138592 17932 126272 214244 0 0 1 18 109 19 2 1 1 96
0 0 138592 17932 126272 214244 0 0 0 0 105 46 0 1 0 99
0 0 138592 17932 126272 214244 0 0 0 0 198 62 40 14 0 45
0 0 138592 17932 126272 214244 0 0 0 0 117 49 0 0 0 100
0 0 138592 17924 126272 214244 0 0 0 176 220 938 3 4 13 80
0 0 138592 17924 126272 214244 0 0 0 0 358 1522 8 17 0 75
1 0 138592 17924 126272 214244 0 0 0 0 368 1447 4 24 0 72
0 0 138592 17924 126272 214244 0 0 0 0 352 1277 9 12 0 79
# vmstat 1
procs memory swap io system cpu
r b swpd free buff cache si so bi bo in cs us sy wa id
2 0 145940 17752 118600 215592 0 1 1 18 109 19 2 1 1 96
2 0 145940 15856 118604 215652 0 0 0 468 789 108 86 14 0 0
3 0 146208 13884 118600 214640 0 360 0 360 498 71 91 9 0 0
2 0 146388 13764 118600 213788 0 340 0 340 672 41 87 13 0 0
2 0 147092 13788 118600 212452 0 740 0 1324 620 61 92 8 0 0
2 0 147360 13848 118600 211580 0 720 0 720 690 41 96 4 0 0
2 0 147912 13744 118192 210592 0 720 0 720 605 44 95 5 0 0
2 0 148452 13900 118192 209260 0 372 0 372 639 45 81 19 0 0
2 0 149132 13692 117824 208412 0 372 0 372 457 47 90 10 0 0
从上面第一个结果可看到,最后一列(id) 表示的是空闲时间,我们可以看到,在基准线统计时,CPU 的空闲时间在79% - 100%.在第二个结果可看到,系统处于100%的占用率以及没有空闲时间.从这个比较中,我们就可以确定是否是CPU 使用率应该被优化.
2.0 安装监控工具
多数 *nix系统都有一堆标准的监控命令.这些命令从一开始就是*nix 的一部分.Linux 则通过基本安装包以及额外包提供了其他监控工具,这些安装包多数都存在各个Linux 发布版本中.尽管还有其他更多的开源以及第三方监控软件,但本文档只讨论基于Linux 发布版本的监控工具.
本章将讨论哪些工具怎样来监控系统性能.
Tool Description Base Repository
vmstat all purpose performance tool yes yes
mpstat provides statistics per CPU no yes
sar all purpose performance monitoring tool no yes
iostat provides disk statistics no yes
netstat provides network statistics yes yes
dstat monitoring statistics aggregator no in most distributions
iptraf traffic monitoring dashboard no yes
netperf Network bandwidth tool no In some distributions
ethtool reports on Ethernet interface configuration yes yes
iperf Network bandwidth tool no yes
tcptrace Packet analysis tool no yes
3.0 CPU 介绍
CPU 利用率主要依赖于是什么资源在试图存取.内核调度器将负责调度2种资源种类:线程(单一或者多路)和中断.调度器去定义不同资源的不同优先权.以下列表从优先级高到低排列:
Interrupts(译注:中断) - 设备通知内核,他们完成一次数据处理的过程.例子,当一块网卡设备递送网络数据包或者一块硬件提供了一次IO 请求.
Kernel(System) Processes(译注:内核处理过程) - 所有内核处理过程就是控制优先级别.
User Processes(译注:用户进程) - 这块涉及”userland”.所有软件程序都运行在这个user space.这块在内核调度机制中处于低优先级.
从上面,我们可以看出内核是怎样管理不同资源的.还有几个关键内容需要介绍,以下部分就将介绍context(译注:上下文切换),run queues(译注:运行队列)以及utilization(译注:利用率).
3.1 上下文切换
多数现代处理器都能够运行一个进程(单一线程)或者线程.多路超线程处理器有能力运行多个线程.然而,Linux 内核还是把每个处理器核心的双核心芯片作为独立的处理器.比如,以Linux 内核的系统在一个双核心处理器上,是报告显示为两个独立的处理器.
一个标准的Linux 内核可以运行50 至 50,000 的处理线程.在只有一个CPU时,内核将调度并均衡每个进程线程.每个线程都分配一个在处理器中被开销的时间额度.一个线程要么就是获得时间额度或已抢先获得一些具有较高优先级(比如硬件中断),其中较高优先级的线程将从区域重新放置回处理器的队列中.这种线程的转换关系就是我们提到的上下文切换.
每次内核的上下文切换,资源被用于关闭在CPU寄存器中的线程和放置在队列中.系统中越多的上下文切换,在处理器的调度管理下,内核将得到更多的工作.
3.2 运行队列
每个CPU 都维护一个线程的运行队列.理论上,调度器应该不断的运行和执行线程.进程线程不是在sleep 状态中(译注:阻塞中和等待IO中)或就是在可运行状态中.如果CPU 子系统处于高负荷下,那就意味着内核调度将无法及时响应系统请求.导致结果,可运行状态进程拥塞在运行队列里.当运行队列越来越巨大,进程线程将花费更多的时间获取被执行.
比较流行的术语就是”load”,它提供当前运行队列的详细状态.系统 load 就是指在CPU 队列中有多少数目的线程,以及其中当前有多少进程线程数目被执行的组合.如果一个双核系统执行了2个线程,还有4个在运行队列中,则 load 应该为 6. top 这个程序里显示的load averages 是指1,5,15 分钟以内的load 情况.
3.3 CPU 利用率
CPU 利用率就是定义CPU 使用的百分比.评估系统最重要的一个度量方式就是CPU 的利用率.多数性能监控工具关于CPU 利用率的分类有以下几种:
User Time(译注:用户进程时间) - 关于在user space中被执行进程在CPU 开销时间百分比.
System Time(译注:内核线程以及中断时间) - 关于在kernel space中线程和中断在CPU 开销时间百分比.
Wait IO(译注:IO 请求等待时间) - 所有进程线程被阻塞等待完成一次IO 请求所占CPU 开销idle的时间百分比.
Idle(译注:空闲) - 一个完整空闲状态的进程在CPU 处理器中开销的时间百分比.
4.0 CPU 性能监控
理解运行队列,利用率,上下文切换对怎样CPU 性能最优化之间的关系.早期提及到,性能是相对于基准线数据的.在一些系统中,通常预期所达到的性能包括:
Run Queues - 每个处理器应该运行队列不超过1-3 个线程.例子,一个双核处理器应该运行队列不要超过6 个线程.
CPU Utiliation - 如果一个CPU 被充分使用,利用率分类之间均衡的比例应该是
65% - 70% User Time
30% - 35% System Time
0% - 5% Idle Time
Context Switches - 上下文切换的数目直接关系到CPU 的使用率,如果CPU 利用率保持在上述均衡状态时,大量的上下文切换是正常的.
很多Linux 上的工具可以得到这些状态值,首先就是 vmstat 和 top 这2个工具.
4.1 vmstat 工具的使用
vmstat 工具提供了一种低开销的系统性能观察方式.因为 vmstat 本身就是低开销工具,在非常高负荷的服务器上,你需要查看并监控系统的健康情况,在控制窗口还是能够使用vmstat 输出结果.这个工具运行在2种模式下:average 和 sample 模式.sample 模式通过指定间隔时间测量状态值.这个模式对于理解在持续负荷下的性能表现,很有帮助.下面就是
vmstat 运行1秒间隔的示例:
# vmstat 1
procs ———–memory———- —swap– —–io—- –system– —-cpu—-
r b swpd free buff cache si so bi bo in cs us sy id wa
0 0 104300 16800 95328 72200 0 0 5 26 7 14 4 1 95 0
0 0 104300 16800 95328 72200 0 0 0 24 1021 64 1 1 98 0
0 0 104300 16800 95328 72200 0 0 0 0 1009 59 1 1 98 0
Table 1: The vmstat CPU statistics
Field Description
r The amount of threads in the run queue. These are threads that are runnable, but the CPU is not available to execute them.
当前运行队列中线程的数目.代表线程处于可运行状态,但CPU 还未能执行.
b This is the number of processes blocked and waiting on IO requests to finish.
当前进程阻塞并等待IO 请求完成的数目
in This is the number of interrupts being processed.
当前中断被处理的数目
cs This is the number of context switches currently happening on the system.
当前kernel system中,发生上下文切换的数目
us This is the percentage of user CPU utilization.
CPU 利用率的百分比
sys This is the percentage of kernel and interrupts utilization.
内核和中断利用率的百分比
wa This is the percentage of idle processor time due to the fact that ALL runnable threads are blocked waiting on IO.
所有可运行状态线程被阻塞在等待IO 请求的百分比
id This is the percentage of time that the CPU is completely idle.
CPU 空闲时间的百分比
4.2 案例学习:持续的CPU 利用率
在这个例子中,这个系统被充分利用
# vmstat 1
procs memory swap io system cpu
r b swpd free buff cache si so bi bo in cs us sy wa id
3 0 206564 15092 80336 176080 0 0 0 0 718 26 81 19 0 0
2 0 206564 14772 80336 176120 0 0 0 0 758 23 96 4 0 0
1 0 206564 14208 80336 176136 0 0 0 0 820 20 96 4 0 0
1 0 206956 13884 79180 175964 0 412 0 2680 1008 80 93 7 0 0
2 0 207348 14448 78800 175576 0 412 0 412 763 70 84 16 0 0
2 0 207348 15756 78800 175424 0 0 0 0 874 25 89 11 0 0
1 0 207348 16368 78800 175596 0 0 0 0 940 24 86 14 0 0
1 0 207348 16600 78800 175604 0 0 0 0 929 27 95 3 0 2
3 0 207348 16976 78548 175876 0 0 0 2508 969 35 93 7 0 0
4 0 207348 16216 78548 175704 0 0 0 0 874 36 93 6 0 1
4 0 207348 16424 78548 175776 0 0 0 0 850 26 77 23 0 0
2 0 207348 17496 78556 175840 0 0 0 0 736 23 83 17 0 0
0 0 207348 17680 78556 175868 0 0 0 0 861 21 91 8 0 1
根据观察值,我们可以得到以下结论:
1,有大量的中断(in) 和较少的上下文切换(cs).这意味着一个单一的进程在产生对硬件设备的请求.
2,进一步显示某单个应用,user time(us) 经常在85%或者更多.考虑到较少的上下文切换,这个应用应该还在处理器中被处理.
3,运行队列还在可接受的性能范围内,其中有2个地方,是超出了允许限制.
4.3 案例学习:超负荷调度
在这个例子中,内核调度中的上下文切换处于饱和
# vmstat 1
procs memory swap io system cpu
r b swpd free buff cache si so bi bo in cs us sy wa id
2 1 207740 98476 81344 180972 0 0 2496 0 900 2883 4 12 57 27
0 1 207740 96448 83304 180984 0 0 1968 328 810 2559 8 9 83 0
0 1 207740 94404 85348 180984 0 0 2044 0 829 2879 9 6 78 7
0 1 207740 92576 87176 180984 0 0 1828 0 689 2088 3 9 78 10
2 0 207740 91300 88452 180984 0 0 1276 0 565 2182 7 6 83 4
3 1 207740 90124 89628 180984 0 0 1176 0 551 2219 2 7 91 0
4 2 207740 89240 90512 180984 0 0 880 520 443 907 22 10 67 0
5 3 207740 88056 91680 180984 0 0 1168 0 628 1248 12 11 77 0
4 2 207740 86852 92880 180984 0 0 1200 0 654 1505 6 7 87 0
6 1 207740 85736 93996 180984 0 0 1116 0 526 1512 5 10 85 0
0 1 207740 84844 94888 180984 0 0 892 0 438 1556 6 4 90 0
根据观察值,我们可以得到以下结论:
1,上下文切换数目高于中断数目,说明kernel中相当数量的时间都开销在上下文切换线程.
2,大量的上下文切换将导致CPU 利用率分类不均衡.很明显实际上等待io 请求的百分比(wa)非常高,以及user time百分比非常低(us).
3,因为CPU 都阻塞在IO请求上,所以运行队列里也有相当数目的可运行状态线程在等待执行.
4.4 mpstat 工具的使用
如果你的系统运行在多处理器芯片上,你可以使用 mpstat 命令来监控每个独立的芯片.Linux 内核视双核处理器为2 CPU’s,因此一个双核处理器的双内核就报告有4 CPU’s 可用.
mpstat 命令给出的CPU 利用率统计值大致和 vmstat 一致,但是 mpstat 可以给出基于单个处理器的统计值.
# mpstat –P ALL 1
Linux 2.4.21-20.ELsmp (localhost.localdomain) 05/23/2006
05:17:31 PM CPU %user %nice %system %idle intr/s
05:17:32 PM all 0.00 0.00 3.19 96.53 13.27
05:17:32 PM 0 0.00 0.00 0.00 100.00 0.00
05:17:32 PM 1 1.12 0.00 12.73 86.15 13.27
05:17:32 PM 2 0.00 0.00 0.00 100.00 0.00
05:17:32 PM 3 0.00 0.00 0.00 100.00 0.00
4.5 案例学习: 未充分使用的处理量
在这个例子中,为4 CPU核心可用.其中2个CPU 主要处理进程运行(CPU 0 和1).第3个核心处理所有内核和其他系统功能(CPU 3).第4个核心处于idle(CPU 2).
使用 top 命令可以看到有3个进程差不多完全占用了整个CPU 核心.
# top -d 1
top - 23:08:53 up 8:34, 3 users, load average: 0.91, 0.37, 0.13
Tasks: 190 total, 4 running, 186 sleeping, 0 stopped, 0 zombie
Cpu(s): 75.2% us, 0.2% sy, 0.0% ni, 24.5% id, 0.0% wa, 0.0% hi, 0.0%
si
Mem: 2074736k total, 448684k used, 1626052k free, 73756k buffers
Swap: 4192956k total, 0k used, 4192956k free, 259044k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
15957 nobody 25 0 2776 280 224 R 100 20.5 0:25.48 php
15959 mysql 25 0 2256 280 224 R 100 38.2 0:17.78 mysqld
15960 apache 25 0 2416 280 224 R 100 15.7 0:11.20 httpd
15901 root 16 0 2780 1092 800 R 1 0.1 0:01.59 top
1 root 16 0 1780 660 572 S 0 0.0 0:00.64 init
# mpstat –P ALL 1
Linux 2.4.21-20.ELsmp (localhost.localdomain) 05/23/2006
05:17:31 PM CPU %user %nice %system %idle intr/s
05:17:32 PM all 81.52 0.00 18.48 21.17 130.58
05:17:32 PM 0 83.67 0.00 17.35 0.00 115.31
05:17:32 PM 1 80.61 0.00 19.39 0.00 13.27
05:17:32 PM 2 0.00 0.00 16.33 84.66 2.01
05:17:32 PM 3 79.59 0.00 21.43 0.00 0.00
05:17:32 PM CPU %user %nice %system %idle intr/s
05:17:33 PM all 85.86 0.00 14.14 25.00 116.49
05:17:33 PM 0 88.66 0.00 12.37 0.00 116.49
05:17:33 PM 1 80.41 0.00 19.59 0.00 0.00
05:17:33 PM 2 0.00 0.00 0.00 100.00 0.00
05:17:33 PM 3 83.51 0.00 16.49 0.00 0.00
05:17:33 PM CPU %user %nice %system %idle intr/s
05:17:34 PM all 82.74 0.00 17.26 25.00 115.31
05:17:34 PM 0 85.71 0.00 13.27 0.00 115.31
05:17:34 PM 1 78.57 0.00 21.43 0.00 0.00
05:17:34 PM 2 0.00 0.00 0.00 100.00 0.00
05:17:34 PM 3 92.86 0.00 9.18 0.00 0.00
05:17:34 PM CPU %user %nice %system %idle intr/s
05:17:35 PM all 87.50 0.00 12.50 25.00 115.31
05:17:35 PM 0 91.84 0.00 8.16 0.00 114.29
05:17:35 PM 1 90.82 0.00 10.20 0.00 1.02
05:17:35 PM 2 0.00 0.00 0.00 100.00 0.00
05:17:35 PM 3 81.63 0.00 15.31 0.00 0.00
你也可以使用 ps 命令通过查看 PSR 这列,检查哪个进程在占用了哪个CPU.
# while :; do ps -eo pid,ni,pri,pcpu,psr,comm | grep ‘mysqld’; sleep 1;
done
PID NI PRI %CPU PSR COMMAND
15775 0 15 86.0 3 mysqld
PID NI PRI %CPU PSR COMMAND
15775 0 14 94.0 3 mysqld
PID NI PRI %CPU PSR COMMAND
15775 0 14 96.6 3 mysqld
PID NI PRI %CPU PSR COMMAND
15775 0 14 98.0 3 mysqld
PID NI PRI %CPU PSR COMMAND
15775 0 14 98.8 3 mysqld
PID NI PRI %CPU PSR COMMAND
15775 0 14 99.3 3 mysqld
4.6 结论
监控 CPU 性能由以下几个部分组成:
1,检查system的运行队列,以及确定不要超出每个处理器3个可运行状态线程的限制.
2,确定CPU 利用率中user/system比例维持在70/30
3,当CPU 开销更多的时间在system mode,那就说明已经超负荷并且应该尝试重新调度优先级
4,当I/O 处理得到增长,CPU 范畴的应用处理将受到影响
下一篇：
Linux System and Performance Monitoring(Memory篇)
同事力作，原文见：http://tonnyom.yo2.cn/2009/08/10/linux-system-and-performance-monitoring-cpu/
Tags: cpu, linux, monitoring, mpstat, performance, toonyom, vmstat, 性能, 监控, 进程上下文
Posted in 操作系统, 管理工具, 运维小技巧 | 2 Comments »
