System io statistics

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       $ cat /proc/diskstats
       
       
   8       0 sda 61956814 17784 10611545630 25247251 81500542 90293241 18537974922 158892176 0 19476563 183932800
       
       
   8       1 sda1 36834 0 711618 8857 1066794 1088773 4311554 5979 0 10784 14759
       
       
   8       2 sda2 61919793 17784 10610832348 25238366 80433748 89204468 18533663368 158886197 0 19467225 183912764
       
       
 253       0 gg-0 5623688 0 126996682 1287038 20634674 0 185895864 1189423 0 1248510 2481206
       
       
 253       1 gg-1 128 0 2136 15 0 0 0 0 0 15 15
       
       
 253       2 gg-2 56342914 0 10483832346 23884963 149036514 0 18347767504 183502049 0 18282017 207482318
      
      
      
      

       
       
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每一列的含义分别为：

• 第一列为 设备号

（number of issued reads. This is the total number of reads completed successfully.）

• 第二列为 次设备号

（number of reads merged）

• 第三列为 设备名称

（number of sectors read. This is the total number of sectors read successfully.）

• 第四列为 成功完成读的总次数

（number of milliseconds spent reading. This is the total number of milliseconds spent by all reads (as measured from __make_request() to end_that_request_last()).）

• 第五列为 Combined reads,为了效率可能会合并相邻的读和写,从而两次4K的读在它最终被处理到磁盘上之前可能会变成一次8K的读,才被计数（和排队）,因此只有一次I/O操作.

（number of writes merged Reads and writes which are adjacent to each other may be merged for efficiency. Thus two 4K reads may become one 8K read before it is ultimately handed to the disk, and so it will be counted (and queued) as only one I/O. This field lets you know how often this was done.）

• 第六列为 读扇区的次数
• 第七列为 time spent reading（ms）,这是所有读操作所花费的毫秒数（用__make_request()到end_that_request_last()测量）
• The eighth to eleventh columns are respectively write
• The twelfth column I/O的当前进度,只有这个域应该是0,如果这个值为0,同时write_complete read_complete io_processing It may be the same foreverIO hang了.

number of I/Os currently in progress. The only field that should go to zero. Incremented as requests are given to appropriate request_queue_t and decremented as they finish.）

• The thirteenth column Enter the time it took to enter（ms）,花在I/O操作上的毫秒数,这个域会增长只要field 9不为0.

（number of milliseconds spent doing I/Os. This field is increased so long as field 9 is nonzero.）

• The fourteenth column 输入/输出操作花费的加权毫秒数,

（number of milliseconds spent doing I/Os. This field is incremented at each I/O start, I/O completion, I/O merge, or read of these stats by the number of I/Os in progress (field 9) times the number of milliseconds spent doing I/O since the last update of this field. This can provide an easy measure of both I/O completion time and the backlog that may be accumulating.）

可以参考：

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       ​​file displays the I/O statistics
       
       
    of block devices. Each line contains the following 14
       
       
    fields:
       
       
     1 - major number
       
       
     2 - minor mumber
       
       
     3 - device name
       
       
     4 - reads completed successfully
       
       
     5 - reads merged
       
       
     6 - sectors read
       
       
     7 - time spent reading (ms)
       
       
     8 - writes completed
       
       
     9 - writes merged
       
       
    10 - sectors written
       
       
    11 - time spent writing (ms)
       
       
    12 - I/Os currently in progress
       
       
    13 - time spent doing I/Os (ms)
       
       
    14 - weighted time spent doing I/Os (ms)​​
      
      
      
      

       
       
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​​/sys/block/device_name/stat​​The output is the same as the fields above.