wiki:jazz/Performance_Tuning

Version 33 (modified by jazz, 14 years ago) (diff)

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  1. Performance Tuning
    1. System Performance Tuning : CPU
    2. System Performance Tuning : Memory
    3. System Performance Tuning : File System
    4. I/O Performance Tuning : NFS
    5. I/O Performance Tuning : IOWait
    6. Network Performance Tuning
    7. Power Management
    8. Security / Management Tip

Performance Tuning

System Performance Tuning : CPU

  • 檢查 CPU 是否為 64 位元的方法 - ​參考自 Ubuntu 論壇 
    ~$ sudo lshw -C cpu | grep width
       width: 32 bits ---> 為 32 位元
=======
       width: 64 bits ---> 為 64 位元
  • 檢查 CPU 是否支援虛擬化 - 旗標(flags)分別是： Intel (vmx) 與AMD (svm) (KVM 安裝 (rock)) 
    ~$ cat /proc/cpuinfo | egrep 'vmx|svm' --color

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 (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] ​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 ​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)

System Performance Tuning : File System

  • 如何調整每個使用者可以開啟的檔案個數
    • [參考] ​Increasing the file descriptor limit
    • [參考] ​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(2010-02-22)

      • /etc/security/limits.conf

        old new  
        4949#ftp             -       chroot          /ftp
        5050#@student        -       maxlogins       4
        5151
         52*      soft        nofile        4096
         53*      hard        nofile        743964
         54
        5255# 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

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 (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

  • 2010-03-31 : 高 IOWait 有什麼好的解決之道呢??

Network Performance Tuning

  • TCP 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 (2010-03-26) 
    echo 30 > /proc/sys/net/ipv4/tcp_fin_timeout 
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：(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

Power Management

  • 啟動 SATA ALPM 電源管理功能 - ​powertop 提供之建議 
    echo min_power > /sys/class/scsi_host/host0/link_power_management_policy
  • 虛擬機器的 clocksource (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 (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