了解/ proc / / io中的计数器

我正在为Munin创build一个插件来监视指定进程的统计信息。 信息来源之一是/proc/[pid]/io 。 但是我很难找出rchar / wcharread_bytes / written_bytes之间的区别。

它们不一样,因为它们提供不同的价值。 他们代表什么?

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尽管proc手册页是悲惨的(如果是大多数手册/关于任何与cookie模式用户空间开发无关的文档),幸运的是,这些内容完全记录在Documentation/filesystems/proc.txt下的Linux内核源代码中 。 这里是相关的位:

 rchar ----- I/O counter: chars read The number of bytes which this task has caused to be read from storage. This is simply the sum of bytes which this process passed to read() and pread(). It includes things like tty IO and it is unaffected by whether or not actual physical disk IO was required (the read might have been satisfied from pagecache) wchar ----- I/O counter: chars written The number of bytes which this task has caused, or shall cause to be written to disk. Similar caveats apply here as with rchar. read_bytes ---------- I/O counter: bytes read Attempt to count the number of bytes which this process really did cause to be fetched from the storage layer. Done at the submit_bio() level, so it is accurate for block-backed filesystems. <please add status regarding NFS and CIFS at a later time> write_bytes ----------- I/O counter: bytes written Attempt to count the number of bytes which this process caused to be sent to the storage layer. This is done at page-dirtying time.