做一件事情,首先要知道自己在干什么,而不是盲目得升級內核,現(xiàn)在升級內核有點泛濫,sigh
       首先讓我們先了解一下2.6內核的新特性
      
一、01.模塊子系統(tǒng)（Module Subsystem）、統(tǒng)一設備模型（Unified Device Model）和 PnP 支持
       模塊子系統(tǒng)發(fā)生了重大變化。
      
    02.穩(wěn)定性有所提高
           為了*避免內核加載或者導出正在被使用的內核模塊，或者至少為了減少加載或者卸載模塊的同時使用該模塊的可能性
       （這有時會導致系統(tǒng)崩潰），內核加載和導出內核模塊的過程都得到了改進。
      
    03.統(tǒng)一設備模型
       統(tǒng)一設備模型的創(chuàng)建是 2.6 內核zui重要的變化之一。它促進了模塊接口的標準化，其目的是更好地控制和管理設備，例如：
      
       更準確地確定系統(tǒng)設備。
       電源管理和設備電源狀態(tài)。
       改進的系統(tǒng)總線結構管理。
      
    04.即插即用（PnP）支持
           1.1.1 和 1.1.2 小節(jié)中提及的變化使得運行 2.6 內核的 LINUX 成為一個真正即插即用的 OS。
       例如，對 ISA PnP 擴展、 MCA 和 EISA 總線以及熱插拔設備的 PnP 支持。
      
    05.內核基礎設施的變化             
       為了區(qū)別以 .o 為擴展名的常規(guī)對象文件，內核模塊現(xiàn)在使用的擴展名是 .ko。
       創(chuàng)建了新的 sysfs 文件系統(tǒng)，當內核發(fā)現(xiàn)設備樹時就會描述它。
       內存支持，NUMA 支持
       支持更大數(shù)量的 RAM      
       2.6 內核支持更大數(shù)量的 RAM，在分頁模式下zui高可達 64GB。
      
    06.NUMA
       對非一致內核訪問（Non-Uniform Memory Access - NUMA）系統(tǒng)的支持是 2.6 內核中新出現(xiàn)的。
      
    07.線程模型，NPTL
       相對于 v2.4 的 LinuxThreads，在版本 2.6 中新出現(xiàn)的是 NPTL（Native POSIX Threading Library）。
       NPTL 為 Linux 帶來了企業(yè)級線程支持，提供的性能遠遠超過了 LinuxThreads。它所基于的用戶與內核線程的比率是 1:1。
      
       在 2003 年 10 月，GNU C 程序庫 glibc 中融入了 NPTL 支持，Red Hat 在 Red Hat Linux 9 和
       Red Hat Enterprise Linux 中使用定制的 v2.4 內核實現(xiàn)了 NPTL。
      
    08.性能改進      
       新的調度器算法
           2.6 Linux 內核引入了新的 O1 算法。在高負載情況下它運行得特別好。新的調度器基于每個 CPU 來分布時間片，
       這樣就消除了全局同步和重新分配循環(huán)，從而提高了性能。
      
       內核搶占（Kernel Preemption）
       新的 2.6 內核是搶占式的。這將顯著地提高交互式和多媒體應用程序的性能。
      
       I/O 性能改進
           Linux 的 I/O 子系統(tǒng)也發(fā)生了重大的變化，通過修改 I/O 調度器來確保不會有進程駐留在隊列中過長時間等待進行輸入/輸出操作，
       這樣就使得 I/O 操作的響應更為迅速。
      
       快速用戶空間互斥（Fast User-Space Mutexes）
          “futexes”（快速用戶空間互斥）可以使線程串行化以避免競態(tài)條件，引入它也提高了響應速度。
       通過在內核空間中部分實現(xiàn)“futexes”以允許基于競爭設置等待任務的優(yōu)先級而實現(xiàn)改進。

    09.擴展性改進      
       處理器數(shù)目更多
       Linux 內核 2.6 zui多可以支持 64 個 CPU。支持更大的內存，歸功于 PAE（物理地址擴展，Physical Address Extensions），在 32-位系統(tǒng)上分頁模式下所支持的內存增加到了 64GB。

       用戶和組
       惟一用戶和組的數(shù)量從 65,000 增至 40 多億，也就是從 16-位增加到了 32-位。

       PID 的數(shù)量
       PID 的zui大數(shù)量從 32,000 增至 10 億。

       打開文件描述符的數(shù)量
       打開文件描述符的數(shù)量沒有增加，但是不再需要事先設置該參數(shù)，它將自行調節(jié)。

    10.支持更多的設備
           在 Linux 內核 2.6 之前，內核中有可以約束大型系統(tǒng)的限制，比如每條鏈 256 個設備。v2.6 內核*地打破了這些限制，
       不但可以支持更多類型的設備，而且支持更多同類型的設備。在 Linux 2.6 系統(tǒng)中，可以支持 4095 種主要的設備類型，
       每一個單獨的類型可以有超過一百萬個子設備。
       文件系統(tǒng)大小
       Linux 內核 2.6 所允許的可尋址文件系統(tǒng)大小zui大為 16 TB。

    11.文件系統(tǒng)
           ext2、ext3 和 ReiserFS 等傳統(tǒng) Linux 文件系統(tǒng)得到了顯著的改進。zui值得注意的改進是擴展屬性（或文件元數(shù)據(jù)）的引入。
       zui重要的是 POSIX ACL 的實現(xiàn)，這是對普通 UNIX 權限的擴展，可以支持更細化的用戶訪問控制。
      
    12.除了對傳統(tǒng) Linux 文件系統(tǒng)的改進支持以外，新的內核*支持在 Linux 中相對較新的 XFS 文件系統(tǒng)。      
       Linux 2.6 內核現(xiàn)在還引入了對 NTFS 文件系統(tǒng)的改進的支持，現(xiàn)在允許以讀/寫模式安裝 NTFS 文件系統(tǒng)。

    基于以上2.6的新特性，我決定用2.6的內核，我的系統(tǒng)為Red Hat Enterprise Linux AS release 3 Taroon Update 3
硬件環(huán)境為DELL 2850

一、下載解壓并打上內核補丁
我以2.6.10為例子，patche以bk4的例子，目的只是讓大家知道怎么打patch，
其實本人用的是2.6.6的內核，因為在AS3.0上升級到2.6.9以上的內核，
mount大的nfs網絡硬盤時，df 顯示不正確，明明是800G的盤變成4.2G，
不過還是能正常用，我升級過nfs和mount的包都沒用，/var/log/message里
提示是kernel: nfs warning: mount version older than kernel，
還望知道的 告知一聲，謝 :    BTW:2.6.8的內核沒用過

    內核源代碼：/pub/linux/kernel/v2.6/linux-2.6.10.tar.bz2
    內核補丁：/pub/linux/ ... atch-2.6.10-bk4.bz2

    cd /usr/src
    rm -rf linux
    tar jxf /download/linux-2.6.10.tar.bz2
    ln -s linux-2.6.10 linux
    cd linux
    bunzip2 -dv /download/patch-2.6.10-bk4.bz2 |patch -p1
    如果在/usr/src目錄下就用patch -p0

二、修改內核源代碼 升級2.6就是為了優(yōu)化，干脆連源代碼也改了吧
  
    1.修改/usr/src/linux/include/linux/posix_types.h
      設置fd_set支持的zui大數(shù)量 
      #define __FD_SETSIZE 1024 --->; 65536    
   
    2.修改/usr/src/linux/include/linux/fs.h
      設置zui大打開文件數(shù)量（TCP連接數(shù)量）
      #define INR_OPEN 1024 --->; 65536
      #define NR_FILE 8192 --->; 65536
      #define NR_RESERVED_FILES 10 --->; 128
    
    3.修改/usr/src/linux/include/net/tcp.h
      設置TIMEOUT的時間為1秒
      #define TCP_TIMEWAIT_LEN 60＊HZ 60 --->; 1＊HZ
      設置在backlog隊列里的半連接的重試次數(shù)，每次都會花相應的時間，本質上 也是減少重試時間
      #define TCP_SYNACK_RETRIES  5 --->; 3

針對RHEL-AS3本來就是穩(wěn)定+優(yōu)化的，不過就算你用 RHEL-AS3 自己的內核，那也要修改一下上面的參數(shù)才好呀 :

三、安裝必要的工具

    1.下載module-init-tools-3.1.tar.bz2
  /pub/linux/ ... t-tools-3.1.tar.bz2
CODE:
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        ./configure --prefix=/
        make moveold
        make all install
        ./generate-modprobe.conf /etc/modprobe.conf
2.下載新的mkinitrd
   ftp://195.220.108.108/linux/6/fe ... d-4.1.18-2.i386.rpm
它需要lvm2 device-mapper
ftp://195.220.108.108/linux/6/fe ... -1.00.19-2.i386.rpm
ftp://195.220.108.108/linux/6/fe ... 00.25-1.01.i386.rpm
如果不更新這個包在make install時會提示以下錯誤：
CODE:
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        No module mptbase found for kernel 2.6.10-bk4, aborting.
        mkinitrd failed
        make[1]: ＊＊＊ [install] Error 1
        make: ＊＊＊ [install] Error 2
安裝lvm2-2.00.25-1.01.i386.rpm時請用rpm -ivh --nodeps package name

四、make menuconfig
CODE:
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01.Code maturity level options         --->;
        [＊] Prompt for development and/or incomplete code/drivers                 
        [＊]   Select only drivers expected to compile cleanly                           
    02.General setup  --->;
        [＊] Support for paging of anonymous memory swap                     
        [＊] System V IPC                                                                
        [＊] POSIX Message Queues                                                        
        [ ] BSD Process Accounting                                                     
        [＊] Sysctl support                                                                
        [ ] Auditing support                                                               
        [ ] Support for hot-pluggable devices                                              
        [＊] Kernel Userspace Events                                                       
        [ ] Kernel .config support                                                        
        [＊] Configure standard kernel features for small systems  --->;  
              [＊]   Load all symbols for debugging/kksymoops                                       
              [ ]     Do an extra kallsyms pass                                                    
              [＊]   Enable futex support                                                           
              [＊]   Enable eventpoll support                                                       
              [ ]   Optimize for size                                                              
              [＊]   Use full shmem filesystem
    03.Loadable module support  --->;        
        [＊] Enable loadable module support                                        
        [＊]   Module unloading                                                       
        [ ]     Forced module unloading                                             
        [ ]   Module versioning support EXPERIMENTAL                              
        [ ]   Source checksum for all modules                                       
        [＊]   Automatic kernel module loading
    04.Processor typefeatures  --->; 
           Subarchitecture Type PC-compatible  --->;  
           Processor family Pentium-4/CeleronP4-based/Pentium-4 M/Xeon  --->;  
       [＊] Generic x86 support                                   
       [ ] HPET Timer Support                                    
       [＊] Symmetric multi-processing support      多CPU              
       8   Maximum number of CPUs 2-255                      
       [＊]   SMT Hyperthreading scheduler support              
       [＊] Preemptible Kernel                     搶占式內核，請選上它   
       [ ] Machine Check Exception                               
       < >; Toshiba Laptop support                                
       < >; Dell laptop support                                   
       < >; /dev/cpu/microcode - In IA32 CPU microcode support 
       < >; /dev/cpu/＊/msr - Model-specific register support      
       < >; /dev/cpu/＊/cpuid - CPU information support            
           Firmware Drivers  --->;                                
           High Memory Support 4GB  --->;         高內存             
       [ ] Allocate 3rd-level pagetables from highmem            
       [ ] Math emulation                                        
       [＊] MTRR Memory Type Range Register support             
       [＊] Enable kernel irq balancing                           
       [ ] Use register arguments EXPERIMENTAL      
    05.Power management options ACPI, APM  --->;    電源管理 自定 偶沒選
    06.Bus options PCI, PCMCIA, EISA, MCA, ISA  --->; 板卡支持  自定
        [＊] PCI support                                                                  
        PCI access mode Any  --->;                                              
        [ ] Message Signaled Interrupts MSIMSI-X                               
        [＊] Legacy /proc/pci interface                                                   
        [＊] PCI device name database                                                     
        [ ] ISA support                                                                  
        [ ] MCA support                                                                  
        < >; NatSemi SCx200 support
    07.Executable file formats  --->;
        [＊] Kernel support for ELF binaries                                              
        ; Kernel support for a.outECOFF binaries                                 
        ; Kernel support for MISC binaries      
    08.Device Drivers  --->;   設備驅動及網絡支持
              Generic Driver Options  --->;  默認
            [＊] Select only drivers that don''t need compile-time external firmware                   
            [＊] Prevent firmware from being built                                    
        Memory Technology Devices MTD  --->;  不選
              Parallel port support  --->;    并行端口   自定偶沒選      
        PlugPlay support  --->;    支持熱插拔 自定偶沒選
              Block devices  --->;
            <＊>; Normal floppy disk support                                    
            < >; Compaq SMART2 support                                         
            < >; Compaq Smart Array 5xxx support                               
            < >; Mylex DAC960/DAC1100 PCI RAID Controller support              
            < >; Micro Memory MM5415 Battery Backed RAM support EXPERIMENTAL 
            ; Loopback device support                                       
            < >;   Cryptoloop Support                                          
            ; Network block device support                                  
            < >; Promise SATA SX8 support                                      
            ; RAM disk support                                              
            16  Default number of RAM disks                                 
            4096 Default RAM disk size kbytes                             
              Source directory of cpio_list                                 
            [ ] Support for Large Block Devices                               
            < >; Packet writing on CD/DVD media                                
                 IO Schedulers  --->;   IO調度器,都選上吧 可以在grub.conf用IO調度哪種方式,后面會講的                            
                     <＊>; Anticipatory I/O scheduler                            
                     <＊>; Deadline I/O scheduler                                
                     <＊>; CFQ I/O scheduler          
              ATA/ATAPI/MFM/RLL support  --->;   ATA設備 自定 偶沒選
              SCSI device support  --->;       SCSI設備 自定我有scsi的設備所以有以下選項
            <＊>; SCSI device support                                                               
            [＊]   legacy /proc/scsi/ support                                                       
            ---   SCSI support type disk, tape, CD-ROM                                           
            <＊>;   SCSI disk support                              
              因為偶式MPT的SCSI，所以以下都沒選,省略之
              Multi-device support RAIDLVM  --->;  支持RAID和LVM邏輯卷  自定
            [＊] Multiple devices driver support RAIDLVM      
            <＊>;   RAID support                                      
            < >;     Linear append mode                            
            <＊>;     RAID-0 striping mode                          
            < >;     RAID-1 mirroring mode                         
            < >;     RAID-10 mirrored striping mode EXPERIMENTAL 
            <＊>;     RAID-4/RAID-5 mode                              
            < >;     RAID-6 mode EXPERIMENTAL                      
            <＊>;     Multipath I/O support                           
            < >;     Faulty test module for MD                       
            <＊>;   Device mapper support                             
            < >;     Crypt target support                            
            < >;     Snapshot target EXPERIMENTAL                  
            < >;     Mirror target EXPERIMENTAL                    
            < >;     Zero target EXPERIMENTAL                
              Fusion MPT device support  --->;    偶的SCSI是這個,所以選了 還是自定              
                                                <＊>; Fusion MPT base + ScsiHost drivers                                 
            40  Maximum number of scatter gather entries                             
            <＊>;   Fusion MPT misc device ioctl driver  
              IEEE 1394 FireWire support  --->;  自定  偶沒選
              I2O device support  --->;     自定  偶沒選
              Networking support  --->;     網絡選項
                              [＊] Networking support                                                                
                 Networking options  --->;                                      
                                                                           <＊>; Packet socket                                                                      
                     [ ]   Packet socket: mmapped IO                                                        
                     < >; Netlink device emulation                                                           
                     <＊>; Unix domain sockets        如果你有網絡就選                                                        
                     < >; PF_KEY sockets                                                                     
                     [＊] TCP/IP networking                                                                  
                     [ ]   IP: multicasting                                                                 
                     [ ]   IP: advanced router                                                              
                     [ ]   IP: kernel level autoconfiguration                                               
                     < >;   IP: tunneling                                                                    
                     < >;   IP: GRE tunnels over IP                                                          
                     [ ] IP: ARP daemon support EXPERIMENTAL                                              
                     [＊] IP: TCP syncookie support disabled per default     能防DOS攻擊,但會降低一點性能,總的說性價比不錯                              
                     < >; IP: AH transformation                                                              
                     < >; IP: ESP transformation                                                             
 ,                    < >; IP: IPComp transformation                                                          
                     < >; IP: tunnel transformation                                                          
                     <＊>; IP: TCP socket monitoring interface                                                
                      IP: Virtual Server Configuration  --->;                   lvs 支持                          
                     < >; The *6 protocol EXPERIMENTAL                                                   
                     [＊] Network packet filtering replaces ipchains  --->;    包過濾省略知道的自己選,不熟悉的都選上            
                                                                                                                 以下都沒選,省略
                                    [ ] Amateur Radio support  --->;                                                       
            < >; IrDA infrared subsystem support  --->;                                           
            < >; Bluetooth subsystem support  --->;                                                 
            [＊] Network device support                                                            
            < >;   Dummy net driver support                這個是nis服務器的吧,不大清楚,沒用過                                        
            <＊>;   Bonding driver support                  雙網卡綁定的                                        
            < >;   EQL serial line load balancing support                                        
            < >;   Universal TUN/TAP device driver support                    
                 ARCnet devices  --->;                                                            
                 Ethernet 10 or 100Mbit  --->;                                                  
                 Ethernet 1000 Mbit  --->;                       
                     < >; Alteon AceNIC/3Com 3C985/NetGear GA620 Gigabit support                                  
                     < >; D-Link DL2000-based Gigabit Ethernet support                                            
                     < >; InR PRO/1000 Gigabit Ethernet support                                              
                     < >; National Semiconduct DP83820 support                                 &n, bsp;                  
                     < >; Packet Engines Hamachi GNIC-II support                                                  
                     < >; Packet Engines Yellowfin Gigabit-NIC support EXPERIMENTAL                             
                     < >; Realtek 8169 gigabit ethernet support                                                   
                     < >; Marvell Yukon Chipset / SysKonnect SK-98xx Support                                      
                     <＊>; Broadcom Tigon3 support   
                以下都沒選,省略  
        ISDN subsystem  --->;                                         
        ephony Support  --->;
        Input device support  --->;                                         
              Character devices  --->;                                              
        I2C support  --->;             
        Dallas''s 1-wire bus  --->;     
        Misc devices  --->;            
        Multimedia devices  --->;      
        Graphics support  --->;        
        Sound  --->;                   
        USB support  --->;             
        MMC/SD Card support  --->;    以上都沒選,需要的自己選
    09.File systems  --->;        文件系統(tǒng)     
        < >; Second extended fs support                                                              
        <＊>; Ext3 journalling file system support                                                  
        [ ]   Ext3 extended attributes                                                            
        [＊] JBD ext3 debugging support                                                          
        < >; Reiserfs support                                                                      
        < >; JFS filesystem support                                                                
        < >; XFS filesystem support                                                                
        < >; Minix fs support                                                                      
        < >; ROM file system support                                                               
        [ ] Quota support                                                                         
        < >; Kernel automounter support                                                            
        <＊>; Kernel automounter version 4 support also supports v3                               
            CD-ROM/DVD Filesystems  --->;                                             
                <＊>; ISO 9660 CDROM file system support                                             
                [ ]   Microsoft Joliet CDROM extensions                                          
                [ ]   Transparent decompression extension                                        
                < >; UDF file system support 
            DOS/FAT/NT Filesystems  --->;             floppy要用到的文件格式
                <＊>; MSDOS fs support                                                                                                                   
                <＊>; VFAT Windows-95 fs support                                                  
                437 Default codepage for FAT NEW                                              
                iso8859-1 Default iocharset for FAT NEW                                       
                < >; NTFS file system support                                                        
            Pseudo filesystems  --->;
                [＊] /proc file system support                             proc文件系統(tǒng)支持                             
                [ ]   /proc/kcore support                                                              
                [ ] /dev file system support OBSOLETE                                                
                [ ] /dev/pts Extended Attributes                                                       
                [＊] Virtual memory file system support former shm fs     虛擬內存支持                            
                [ ]   tmpfs Extended Attributes                                                        
                [ ] HugeTLB file system support                                                             
            Miscellaneous filesystems  --->;                                     
            Network File Systems  --->;                                                        
                <＊>; NFS file system support                      nfs客戶端支持                                                            
                [＊]   Provide NFSv3 client support                                                                           
                [ ]   Provide NFSv4 client support EXPERIMENTAL                                                            
                [ ]   Allow direct I/O on NFS files EXPERIMENTAL                                                           
                < >; NFS server support                           nfs服務端支持                                                           
                < >; Secure RPC: Kerberos V mechanism EXPERIMENTAL                                                          
                < >; Secure RPC: SPKM3 mechanism EXPERIMENTAL                                                               
                < >; SMB file system support to mount Windows shares etc.       samba支持                                            
                < >; CIFS support advanced network filesystem for Samba, Windowother CIFS compliant servers            
                < >; NCP file system support to mount NetWare volumes                                                       
                < >; Coda file system support advanced network fs                                                           
                < >; Andrew File System support AFS Experimental                  
            Partition Types  --->;      
            Native Language Support  --->;                 自己選    
    10.Profiling support  --->;                             沒選                                             
    11.Kernel hacking  --->;                                沒選                                                                                            
    12.Security options  --->;                              沒選
    13.Cryptographic options  --->;                         沒選  
    14.Library routines  --->;                                       
         < >; CRC-CCITT functions                               
         <＊>; CRC32 functions                                   
         ; CRC32c Castagnoli, et al Cyclic Redundancy-Check
五、編譯安裝
    步驟:make -jnn代表同時編譯的進程,可以加快編譯速度,n由你的配置決定,我的配置用15-25
         make modules_install
         make install

六、grub的設置
    設置之前先介紹一下2.6的I/O調度器
        2.6包含的四個I/O調度器分別是No-op I/O scheduler、Anticipatory I/O scheduler、Deadline I/O scheduler與CFQ I/O scheduler。
    在后文中分別簡稱為ns、as、ds與cfq。

        ns是一個簡化的調度程序它只作zui基本的合并與排序。與桌面系統(tǒng)的關系不是很大，主要用在一些特殊的軟件
    與硬件環(huán)境下，這些軟件與硬件一般都擁有自己的調度機制對內核支持的要求很小，這很適合一些嵌入式系統(tǒng)環(huán)境。作為桌面用戶我們一般不會選擇它。

        as是當前內核中默認的I/O調度器。它擁有非常好的性能，在2.5中它就相當引人注意。在與2.4內核進行的對比測試中，在2.4中多項以分鐘為單位
    完成的任務，它則是以秒為單位來完成的。正因為如此它成為目前2.6測試版中默認的I/O調度器。但它也存在著弱點，它本身是比較龐大與復雜的，
    在一些特殊的情況下，特別是在數(shù)據(jù)吞吐量非常大的數(shù)據(jù)庫系統(tǒng)中它會變的比較緩慢。

        ds就是針對as的缺點進行改善而來的，還處于測試階段，但已經很穩(wěn)定了。目前表現(xiàn)出的性能幾乎與as一樣好。加之比as更加小巧，
    是相當有前途的調度器，值得一試：

        cfq為系統(tǒng)內的所有任務分配相同的帶寬，提供一個公平的工作環(huán)境，它比較適合桌面環(huán)境。事實上在測試中它也有不錯的表現(xiàn)，
    mplayer xmms等多媒體播放器與它配合的相當好，回放平滑幾乎沒有因訪問磁盤而出現(xiàn)的跳幀現(xiàn)象。對于喜歡在Linux下聽音樂看電影的朋友不妨嘗試一下。
   
    好了，下面說說怎么設置：參數(shù)的格式為elevator=調度器名

    修改/boot/grub/grub.conf,在kernel那行后門加入elevator=deadline
   
    例如：kernel /boot/vmlinuz-2.6.10-bk4 ro root=/dev/你的根分區(qū) elevator=deadline

七、reboot