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如手册页中所描述的，svctm 的 iostat 输出是否可靠？

Solution In Progress - Updated -

Issue

  • 以下是 iostat 手册页的一部分。它提供了一个警告，并指示 svctm 字段将在以后的 sysstat 版本中被删除。

    # man iostat 
    :
    svctm     The average service time(in milliseconds) for I/O requests that were issued to the device.
    Warning! Do not trust this field any more. This field will be removed in a future sysstat version.

  • 如果 iostat 中的 svctm 的输出无法被信任，是否有除 svctm 字段的其它字段或工具？

  • iostat 输出显示 await 比 svctm 大很多。网上还有其他 Linux 文档指出，由于 await 时间是操作系统级的等待，svctm 是磁盘响应时间，那么这意味着 await - svctm 是 linux 内核开销，数字显示一个内核 bug 或需要调优。这是否正确？

Environment

  • Red Hat Enterprise Linux 9
  • Red Hat Enterprise Linux 8
  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 6
  • 例外 ：
    • RHEL 9
      • 由于其通常不可靠的性质，从 RHEL 9 开始，svctm 列已从 iostat 输出中删除了。systats mvapich git 存储库：
        2018/12/14: Version 12.1.2 - Sebastien Godard (sysstat  orange.fr)
        * iostat/sar: Remove service time (svctm) metric.Service time value (displayed as svctm by sar and iostat) could no
        longer be trusted and has been made obsolete for several years. So
        remove it now from sar (sar -d) and iostat output.

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