1、nfile,maxfiles_lim,nproc参数说明
nfile：系统所有经常可打开的最大文件数量
maxfiles_lim：单进程可打开的最大文件数量
nproc: 系统可并发运行的进程数量
执行man nfile(maxfiels_lim,nproc)可获取更详细的信息

2、查看当前nfile参数的值，默认值为0，表示不限制
db178.cm2:/home/fengjing/kmif>#kctune -v nfile
Tunable             nfile
Description         Maximum number of file descriptors (system-wide)
Module              fs_filedscrp
Current Value       330800 [(21*nproc+204800)]
Value at Next Boot  330800 [(21*nproc+204800)]
Value at Last Boot  330800
Default Value       0
Constraints         nfile == 0 or nfile >= 2048
                    nfile <= 2147483647
Can Change          Immediately or at Next Boot
补充：执行kctune -v maxfiles_lim和kctune -v nproc可查看想参数的值

3、查看当前nfile的使用情况
3.1 sar -v命令
00:00:01 text-sz  ov  proc-sz  ov  inod-sz  ov  file-sz  ov
00:05:00   N/A   N/A 1263/6000  0  2315/52096 0  208980/330800 0
00:10:00   N/A   N/A 1249/6000  0  2306/52096 0  208839/330800 0
......
11:25:00   N/A   N/A 1445/6000  0  2422/52096 0  287402/330800 0
11:30:01   N/A   N/A 1427/6000  0  2407/52096 0  280057/330800 0
11:35:00   N/A   N/A 1437/6000  0  2411/52096 0  279036/330800 0
其中:file-sz为279036/330800，即表示当前打开的文件数量是279036，nfile参数的值是330800
3.2 glance命令
然后输入“H”，再输入“t”,可得如下界面：
System Table                 Available        Used      Utilization      High(%)
--------------------------------------------------------------------------------
Proc Table (nproc)               4096          352            9            9
File Table (nfile)             661600         4816            1            1
Shared Mem Table (shmmni)        4096           10            0            0
Message Table (msgmni)           4096            2            0            0
Semaphore Table (semmni)         8192           32            0            0
File Locks (nflocks)             8192           39            0            0
Pseudo Terminals (npty)            60            0            0            0
Buffer Headers (nbuf)              na         1978           na           na

4、动态设置nfile参数值，不影响在线业务
执行kctune nfile=xxxx命令，当前生效且重启也生效，下面信息中也提示，该参数建议使用默认值
db178.cm2:/home/fengjing/kmif>#kctune nfile=661600
     ==> Update the automatic 'backup' configuration first? y
       * The automatic 'backup' configuration has been updated.
       * Future operations will update the backup without prompting.
WARNING: The tunable nfile has been deprecated and should not be tuned
         to a non-default value.  See nfile(5) for details on this
         tunable.
       * The requested changes have been applied to the currently
         running configuration.
Tunable             Value  Expression         Changes
nfile    (before)  330800  (21*nproc+204800)  Immed
         (now)     661600  661600            
db178.cm2:/home/fengjing/kmif>#