[[PageOutline]] * [http://www.brendangregg.com/linuxperf.html Linux Performance] * [[Image(http://www.brendangregg.com/Perf/linux_observability_tools.png,width=800)]] * [[Image(http://www.brendangregg.com/Perf/linux_observability_sar.png,width=800)]] * [[Image(http://www.brendangregg.com/Perf/linux_benchmarking_tools.png,width=800)]] * [[Image(http://www.brendangregg.com/Perf/linux_tuning_tools.png,width=800)]] * [參考] http://www.ufsdump.org/ - 這個網站有許多關於效能調校的細部說明 * [參考] [http://people.redhat.com/alikins/system_tuning.html System Tuning Info for Linux Servers] （有點舊了） * [文件] [http://www.redbooks.ibm.com/redpapers/pdfs/redp4285.pdf Linux Performance and Tuning Guidelines - IBM Redbooks(PDF)] * [文件] [http://www.eslim.co.kr/pds/pds/2/5/RHEL_Tuning_Guide.pdf Red Hat Enterprise Linux Performance Tuning Guide (PDF)] * [工具] 以下是 http://www.ufsdump.org/ 文件中提到的幾個工具 * system & disk I/O * [http://packages.debian.org/procps procps] - /usr/bin/vmstat * [http://packages.debian.org/sysstat sysstat] - /usr/bin/mpstat, /usr/bin/pidstat, /usr/bin/iostat, /usr/bin/sar.sysstat = /usr/bin/sar (由 /etc/alternatives/sar 產生) * [http://packages.debian.org/dstat dstat] * [http://dag.wieers.com/home-made/dstat/ 官方網站] * [http://packages.debian.org/iotop iotop] - 可以觀察 I/O 哪裡發生的通量（throughput）較高 * [http://linux.die.net/man/1/ionice ionice] - 可以修改 I/O 的優先順序 * network * [http://packages.debian.org/iptraf iptraf] * [http://packages.debian.org/iperf iperf] * [http://packages.debian.org/ethtool ethtool] * [簡介] [http://www.linux-mag.com/id/7783 Give Me Liberty or Give Me Eth] * [官網] http://sourceforge.net/projects/gkernel/ * [工具] [http://www.opensourcetesting.org/performance.php Open Source Performance Test Tools] 列舉了許多自由軟體相關的效能測試工具 * [工具] [http://h30565.www3.hp.com/t5/Feature-Articles/16-Linux-Server-Monitoring-Commands-You-Really-Need-To-Know/ba-p/1936 16 Linux Server Monitoring Commands You Really Need To Know] * [參考] [http://kezeodsnx.pixnet.net/blog/post/25428632 Performance tuning] * [參考] [http://www.billhance.com/computers/Linux/pdf/RHEL_Tuning_Guide.pdf Linux performance tuning guide] (Redhat, PDF) * [參考] [http://alephnull.com/perf.html Linux Performance and Development Tools] - 列舉了許多自由軟體的效能分析工具（Performance Analysis Tools） * [參考] [http://dtrace.org/blogs/brendan/2012/03/07/the-use-method-linux-performance-checklist/ The USE Method: Linux Performance Checklist] - 列舉了效能調校的檢查清單 * [參考] [http://highscalability.com/blog/2012/5/16/big-list-of-20-common-bottlenecks.html Big List of 20 Common Bottlenecks] - 效能瓶頸大致上可以歸納為 20 個情境 = Performance Tuning = == System Performance Tuning : CPU == * 檢查 CPU 是否為 64 位元的方法 - [http://ubuntuforums.org/archive/index.php/t-573630.html 參考自 Ubuntu 論壇] * <參考> [http://www.cyberciti.biz/faq/linux-how-to-find-if-processor-is-64-bit-or-not/ Linux: Find If Processor (CPU) is 64 bit / 32 bit] {{{ ~$ sudo lshw -C cpu | grep width width: 32 bits ---> 為 32 位元 ======= width: 64 bits ---> 為 64 位元 }}} {{{ $ getconf LONG_BIT 64 }}} {{{ ~$ grep flags /proc/cpuinfo | grep " lm " --color }}} {{{ ~$ grep -o -w 'lm' /proc/cpuinfo | sort -u lm }}} * 檢查 CPU 是否支援虛擬化 - 旗標(flags)分別是： Intel (vmx) 與AMD (svm) ([wiki:KVM/install KVM 安裝 (rock)]) {{{ ~$ cat /proc/cpuinfo | egrep 'vmx|svm' --color }}} * 執行時間過久： {{{ [1786800.621065] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. }}} == System Performance Tuning : Memory == * 查詢記憶體時脈與單一條的大小 {{{ $ sudo dmidecode 搜尋 Memory Device 會看到類似的結果 Memory Device Array Handle: 0x1000 Error Information Handle: Not Provided Total Width: 64 bits Data Width: 64 bits Size: 2048 MB Form Factor: DIMM Set: None Locator: DIMM_4 Bank Locator: Not Specified Type: DDR2 Type Detail: Synchronous Speed: 800 MHz (1.2 ns) Manufacturer: 7F4F000000000000 Serial Number: 0007D1E4 Asset Tag: 540834 Part Number: TS256MLQ64V8U }}} * Share Memory - 有些程式需要用到比較多 Share Memory (共享記憶體), 如: Kerrighed ([wiki:krg_tuning 2008-03-20 (rock/rider)]) {{{ echo "kernel.shmall = 796917578" >> /etc/sysctl.conf echo "kernel.shmmax = 796917578" >> /etc/sysctl.conf echo "kernel.shmmni = 4096" >> /etc/sysctl.conf }}} * Cache Memroy - [參考] [http://www.codemud.net/~thinker/GinGin_CGI.py/show_id_doc/419 回收 Linux cached memory] * 設定 vm.drop_caches 觸發 kernel 回收用於 cache 的記憶體。 至於 1, 2, 3 的等級，可參考 [http://www.linuxinsight.com/proc_sys_vm_drop_caches.html LinuxInsight 的說明] * 1: free pagecache * 2: free dentries and inodes * 3: free pagecache, dentries and inodes {{{ echo 1 > /proc/sys/vm/drop_caches }}} {{{ sysctl -w vm.drop_caches=1 }}} * 設定 vm.vfs_cache_pressure 使 kernel 更勤於回收 cache。 {{{ sysctl -w vm.vfs_cache_pressure=n (n > 100) }}} * 如何清除使用中的 SWAP 呢？（把 SWAP 的內容釋放出來） - <參考> [http://superuser.com/questions/115565/how-do-i-free-virtual-memory-in-ubuntu How do I free virtual memory in Ubuntu?] {{{ sudo swapoff -a sudo swapon -a }}} * 關於 /proc/sys/vm/swappiness 或 vm.swappiness （[wiki:jazz/11-02-27 2011-02-27]） * 代表意義：Aggressiveness of swapping * 數值範圍：0 ~ 100，通常預設值為 60 （越高越積極搬 SWAP） * 0 : 除非有必要才把虛擬記憶體搬到 SWAP * 100 : 非常頻繁地將虛擬記憶體（VIRT）搬到 SWAP * <參考> [http://distilledb.com/blog/archives/date/2009/02/22/swap-files-in-linux.page Understanding swap files in Linux] * 如何加速桌面應用 - <參考> [http://rudd-o.com/en/linux-and-free-software/tales-from-responsivenessland-why-linux-feels-slow-and-how-to-fix-that Tales from responsivenessland: why Linux feels slow, and how to fix that] * 不過這樣的設定不能用在 VM Server 上，會讓 VM Server 的記憶體很快被用完。 {{{ sysctl -w vm.swappiness=1 sysctl -w vm.vfs_cache_pressure=50 }}} * （[wiki:jazz/11-02-27 2011-02-27]） * 從「[http://stackoverflow.com/questions/561245/virtual-memory-usage-from-java-under-linux-too-much-memory-used Virtual Memory Usage from Java under Linux, too much memory used]」這篇討論，學到一個指令：pmap，隸屬於 [http://packages.debian.org/procps procps 套件]中。用法是 pmap -x $PID (不同身份時，得透過 sudo 取得記憶體狀態） {{{ procps: /usr/bin/pmap }}} {{{ ~$ sudo pmap -x $PID }}} {{{ jazz@drbl:~$ sudo pmap 24972 24972: /usr/bin/php5-cgi 0000000000400000 5144K r-x-- /usr/bin/php5-cgi 0000000000b06000 356K rw--- /usr/bin/php5-cgi 0000000000b5f000 32K rw--- [ anon ] 00000000010da000 2212K rw--- [ anon ] 00007f418a02b000 40K r-x-- /lib/libnss_files-2.7.so 00007f418a035000 2048K ----- /lib/libnss_files-2.7.so 00007f418a235000 8K rw--- /lib/libnss_files-2.7.so 00007f418a237000 28K r-x-- /usr/lib/php5/20060613/pdo_mysql.so 00007f418a23e000 2044K ----- /usr/lib/php5/20060613/pdo_mysql.so 00007f418a43d000 4K rw--- /usr/lib/php5/20060613/pdo_mysql.so ... 略 ... }}} == System Performance Tuning : File System == * ([wiki:jazz/10-05-11 2010-05-11]) * 如何調整每個使用者可以開啟的檔案個數 * [參考] [http://www.xenoclast.org/doc/benchmark/HTTP-benchmarking-HOWTO/node7.html Increasing the file descriptor limit] * [參考] [http://www.netadmintools.com/art295.html GNU/Linux - How Many Open Files?] * 注意：修改 /etc/security/limits.conf 中間必須確定是 TAB ，如果有設定 vim 的 softwaretab 的話，得特別當心!!! * /proc/sys/fs/file-max - 核心預設最多可以開啟的檔案個數 {{{ ~$ cat /proc/sys/fs/file-max 743964 }}} * 修改方法: 使用 sysctl 指令或編輯 /etc/sysctl.conf {{{ sysctl -w fs.file-max=100000 }}} * /proc/sys/fs/file-nr - 目前已開啟檔案個數、可供開啟檔案個數、總開啟檔案上限 {{{ [root@srv-4 proc]# cat /proc/sys/fs/file-nr 3391 969 52427 | | | | | | | | maximum open file descriptors | total free allocated file descriptors total allocated file descriptors (the number of file descriptors allocated since boot) }}} * /etc/security/limits.conf - 每個程序(process)可以開啟檔案的個數(number limits of open files per process) - 像 HDFS 的 !DataNode 就需要調整這種參數([wiki:jazz/10-02-22#Hadoop:HDFS 2010-02-22]) {{{ #!diff --- /etc/security/limits.conf 2010-02-22 11:29:11.000000000 +0800 +++ /etc/security/limits.conf.new 2010-02-22 11:28:33.000000000 +0800 @@ -49,4 +49,6 @@ #ftp - chroot /ftp #@student - maxlogins 4 +* soft nofile 4096 +* hard nofile 743964 + # End of file }}} * /etc/pam.d/login - 告訴系統要用 /etc/security/limits.conf 來設定一些上限 {{{ # Sets up user limits according to /etc/security/limits.conf # (Replaces the use of /etc/limits in old login) session required pam_limits.so }}} * 指令: ulimit - 可以告訴你一些系統限制，並且設定想要的値 {{{ jazz@Wdebian:~$ ulimit -a core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited scheduling priority (-e) 0 file size (blocks, -f) unlimited pending signals (-i) 72704 max locked memory (kbytes, -l) 32 max memory size (kbytes, -m) unlimited open files (-n) 1024 pipe size (512 bytes, -p) 8 POSIX message queues (bytes, -q) 819200 real-time priority (-r) 0 stack size (kbytes, -s) 8192 cpu time (seconds, -t) unlimited max user processes (-u) 72704 virtual memory (kbytes, -v) unlimited file locks (-x) unlimited }}} * 假設 /proc/sys/fs/file-max 跟 /etc/security/limits.conf 都有設定上限為 743964，且 /etc/pam.d/login 也有打開，但是 ulimit -a 指令仍顯示 1024 (預設)，可以修改 /etc/rc.local 或 /etc/profile 強制用 ulimit -n 743964 來提高開檔個數。 {{{ ~$ ulimit -n 743964 }}} * [備註] 如果 ulimit 超出可容許範圍，會顯示 Operation not permitted，此時請檢查相關設定値 {{{ ~$ ulimit -n 7439640 -bash: ulimit: open files: cannot modify limit: Operation not permitted }}} * 如果遇到以上情形，請改用 - [http://unix.stackexchange.com/questions/31679/ulimit-pickle-operation-not-permitted-and-command-not-found 參考來源] {{{ ~$ ulimit -Sn unlimited }}} * [http://www.hadoop.tw/rafan/2008/09/ 幫 Hadoop HDFS 調整系統資源限制] {{{ #!diff --- /etc/security/limits.conf 2010-02-22 11:29:11.000000000 +0800 +++ /etc/security/limits.conf.new 2010-02-22 11:28:33.000000000 +0800 @@ -49,4 +49,6 @@ #ftp - chroot /ftp #@student - maxlogins 4 +* soft nofile 8192 + # End of file }}} * [參考] http://lzone.de/cheat-sheet/ulimit * 指令: prlimit - 可以告訴你特定 process 的限制，並且設定想要的値 {{{ $ sudo prlimit --pid 641 --nofile=743964:743964 $ sudo prlimit --pid 641 RESOURCE DESCRIPTION SOFT HARD UNITS AS address space limit unlimited unlimited 位元組 CORE max core file size 0 unlimited blocks CPU CPU time unlimited unlimited seconds DATA max data size unlimited unlimited 位元組 FSIZE max file size unlimited unlimited blocks LOCKS max number of file locks held unlimited unlimited MEMLOCK max locked-in-memory address space 65536 65536 位元組 MSGQUEUE max bytes in POSIX mqueues 819200 819200 位元組 NICE max nice prio allowed to raise 0 0 NOFILE max number of open files 743964 743964 NPROC max number of processes 56030 56030 RSS max resident set size unlimited unlimited pages RTPRIO max real-time priority 0 0 RTTIME timeout for real-time tasks unlimited unlimited microsecs SIGPENDING max number of pending signals 56030 56030 STACK max stack size 8388608 unlimited 位元組 }}} * 低階指令: 直接查 procfs {{{ cat /proc//limits }}} == I/O Performance Tuning : NFS == * NFS Tuning - /etc/fstab - 加大 NFS read/write size 可以提升檔案系統的 I/O 效率 ([wiki:krg_tuning 2008-03-20 (rock/rider)]) {{{ 192.168.0.111:/home /home nfs rw,bg,soft,intr,rsize=262144,wsize=262144 0 4 192.168.0.111:/opt /opt nfs ro,bg,soft,intr,rsize=262144,wsize=262144 0 4 192.168.0.111:/usr /usr nfs ro,bg,soft,intr,rsize=262144,wsize=262144 0 4 }}} == I/O Performance Tuning : IOWait == * [wiki:jazz/10-03-31 2010-03-31] : 高 IOWait 有什麼好的解決之道呢?? * [http://www.scriptbits.net/2009/07/how-to-identify-what-processes-are-generating-io-wait-load/ How to identify what processes are generating IO Wait load?] {{{ Jun run "pidstat -d 5" and it will print the list of processes doing IO over the last 5 seconds. }}} * [http://ubuntuforums.org/showthread.php?t=1382161 Re: Major problems: High Iowait. Change filesystem from etx4 to xfs/ext3/jfs?] {{{ vm.dirty_writeback_centisecs=100 vm.dirty_expire_centisecs=100" }}} * [http://ubuntuforums.org/showthread.php?t=200004 iowait problem] - 顯示了使用 vmstat , iostat , hdparm 的技巧 * 在 Linux 底下查硬碟型號(hard disk model and serial number) * [參考一] [http://taiwanwolf.blogspot.com/2009/02/linux.html 查看 Linux 系統資訊常用指令] * [參考二] [http://www.cyberciti.biz/faq/linux-getting-scsi-ide-harddisk-information/ Linux: Find out serial / model number and vendor information for SATA and IDE hard disk] * [參考三] [http://dbaspot.com/forums/linux-misc/245398-hard-disk-model-manufacturer.html Hard-disk model and manufacturer - linux-misc] * [工具一] hdparm - [http://packages.debian.org/hdparm Debian 有 hdparm 套件] - 可以拿來測試硬碟效能 {{{ jazz@Wdebian:~$ sudo apt-get install hdparm jazz@Wdebian:~$ sudo hdparm -I /dev/sda | grep "Model Number" Model Number: ST31500341AS }}} * 如果要測試硬碟 I/O 速度，可以用 '''hdparm -t''' {{{ sudo hdparm -t /dev/sda sudo hdparm -T /dev/sda sudo hdparm --direct -t /dev/sda sudo hdparm --direct -T /dev/sda }}} * [工具二] smartctl - [http://packages.debian.org/smartmontools Debian 有 smartmontools 套件] - [http://unixfoo.blogspot.com/2007/11/disk-information-using-smartctl.html 也可以拿來測試硬碟效能] {{{ jazz@Wdebian:~$ sudo apt-get install smartmontools jazz@Wdebian:~$ sudo smartctl -a /dev/sda | grep "Device Model:" Device Model: ST31500341AS }}} * [低階指令一] 如果是 SCSI 或 SATA 硬碟，可以查 /proc/scsi/scsi {{{ jazz@Wdebian:~$ cat /proc/scsi/scsi Attached devices: Host: scsi0 Channel: 00 Id: 00 Lun: 00 Vendor: ATA Model: ST31500341AS Rev: CC1H Type: Direct-Access ANSI SCSI revision: 05 Host: scsi1 Channel: 00 Id: 00 Lun: 00 Vendor: TSSTcorp Model: DVD-ROM TS-H353B Rev: D500 Type: CD-ROM ANSI SCSI revision: 05 Host: scsi2 Channel: 00 Id: 00 Lun: 00 Vendor: ATA Model: ST3640323AS Rev: SD35 Type: Direct-Access ANSI SCSI revision: 05 }}} * [低階指令二] 如果是 IDE 硬碟，可以查 /proc/ide/hd*/model {{{ jazz@lenny:~$ sudo cat /proc/ide/hda/model VBOX HARDDISK }}} == Network Performance Tuning == * TCP Tuning - ([wiki:krg_tuning 2008-03-20 (LSI)]) {{{ echo 262144 > /proc/sys/net/core/rmem_default echo 8388608 > /proc/sys/net/core/wmem_max echo 8388608 > /proc/sys/net/core/rmem_max echo "4096 87380 4194304" > /proc/sys/net/ipv4/tcp_rmem echo "4096 65536 4194304" > /proc/sys/net/ipv4/tcp_wmem }}} * TCP TIME_WAIT & Reuse - 適用網站伺服器 ([wiki:jazz/Trac_Updates#a2010-03-26 2010-03-26]) {{{ sysctl net.ipv4.tcp_fin_timeout=10 sysctl net.ipv4.tcp_tw_reuse=1 sysctl net.ipv4.tcp_tw_recycle=1 }}} * 如果沒辦法 ping 224.0.0.1 的話，代表 Broadcast ICMP 封包被濾掉了，因為預設 Linux kernel 2.6 是 disable 的。解法如下：([wiki:jazz/09-09-07 2009-09-07]) {{{ echo "0" > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts }}} {{{ ~# echo "net.ipv4.icmp_echo_ignore_broadcasts = 0" >> /etc/sysctl.conf ~# sysctl -p net.ipv4.ip_forward = 1 net.ipv4.icmp_echo_ignore_broadcasts = 0 }}} * [http://fourdollars.blogspot.com/2009/04/linux-system.html 如何在 Linux System 當中偵測網路線是否有接上？] ([wiki:jazz/09-05-05 2009-05-05]) {{{ $ cat /sys/class/net/eth0/carrier }}} == Power Management == * 啟動 SATA ALPM 電源管理功能 - [http://packages.debian.org/powertop powertop] 提供之建議 {{{ echo min_power > /sys/class/scsi_host/host0/link_power_management_policy }}} * 虛擬機器的 clocksource ([wiki:jazz/Trac_Updates#a2010-02-11 2010-02-11]) {{{ echo acpi_pm > /sys/devices/system/clocksource/clocksource0/current_clocksource }}} * 直接修改系統參數讓 Linux 休眠 ([wiki:rock/drbl_switch 2010-03-03 (rock)]) {{{ # echo 4 > /proc/acpi/sleep /** 適用 Kernel 2.4 (swsusp)**/ # echo disk > /sys/power/state /** 適用 Kernel 2.4 & 2.6 (swsusp)**/ }}} == Security / Management Tip == * [緣起] 有時因為 Kernel 顯示 DEBUG 訊息，縱使下 reboot 或 shutdown, halt 都無效時，可以使用這個技巧。 * [備忘] 強迫重新開機 - 使用以下指令或按下 ALT + !SysRq + b {{{ echo 1 > /proc/sys/kernel/sysrq echo b > /proc/sysrq-trigger }}} * [備忘] 強迫直接關機 - 使用以下指令或按下 ALT + !SysRq + o {{{ echo 1 > /proc/sys/kernel/sysrq echo o > /proc/sysrq-trigger }}} * 關於 /proc/sysrq-trigger ([wiki:jazz/09-11-17 2009-11-17]) * [http://www.redhat.com/docs/manuals/enterprise/RHEL-4-Manual/en-US/Reference_Guide/s2-proc-sysrq-trigger.html Redhat 手冊的說明 - /proc/sysrq-trigger] * 其實除了 CTRL+ALT+DEL 外，Linux 還可以透過 [http://en.wikipedia.org/wiki/SysRq System Request (Sys Rq) 按鍵] 來做一些特殊除錯工作。這個 Sys Rq 鍵，通常跟 Print Screen 鍵做在一起。 * 要啟用這個功能，首先必須確認核心的 CONFIG_MAGIC_SYSRQ 參數是否有 enable。 * [http://en.wikipedia.org/wiki/Magic_SysRq_key 維基百科除了說明 SYSRQ 可以做哪些事情]外，還介紹了[http://julien.danjou.info/sysrqd/ sysrqd]這個軟體，讓管理者可以遠端執行 SYSRQ 的指令。PS.[http://packages.debian.org/sysrqd sysrqd 也有 debian 套件]!! * 關於 /proc/sys/kernel/sysrq ([wiki:jazz/09-11-17 2009-11-17]) * [http://www.redhat.com/docs/manuals/enterprise/RHEL-4-Manual/en-US/Reference_Guide/s3-proc-sys-kernel.html Redhat 手冊的說明 - /proc/sys/kernel/ 底下的檔案意涵] * [http://lxr.linux.no/#linux+v2.6.31/Documentation/sysrq.txt Linux 核心關於 SysRq 的說明] * [備忘] [http://www.vpsee.com/2010/08/reboot-linux-after-a-kernel-panic/ Linux 遇到 kernel panic 後可自動重新開機(Auto Reboot)] {{{ #!sh $ sudo sysctl -w kernel.panic = 20 }}} 或者編輯 /etc/sysctl.conf 加入 {{{ kernel.panic = 20 }}}