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when a part of Linux Kernel is compiled as a module on could read available parameters with modinfo and set them when loading with modprobe.

Is it possible to get the values of paramters of something that is configured as part of the kernel?

In particular TCP Cubic is not a module on Ubuntu. Cubic contains a parameter hystart to enable and disable hybrid slow start and two more parameters that affect its behavior. Can I somehow read the values of these parameters?

2 Answers 2

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You can find the module parameters in /sys/module/tcp_cubic/parameters no matter whether tcp_cubic is built as a module or into the kernel.

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Are you aware of sysctl ? try sysctl -a | grep tcp

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  • yes, the only two cubic parameter there are that cubic is available and that cubic is used by default. as far as I understand these parameters control general tcp code and not particular congestion contorl algorithm
    – Effie
    Sep 10, 2015 at 14:19
  • The kernel tunables are accessible via sysctl as Nikolaidis mentioned; and in some cases, changing values in /sys or /proc (temporary). To change the behavior of one of the congestion control algo's, you would need to recompile the kernel.
    – Aaron
    Sep 10, 2015 at 16:33
  • according to another answer the second part of your statement seems to be not true, the parameters in /sys/module/tcp_cubic/parameters are writable
    – Effie
    Sep 11, 2015 at 8:42
  • -1, this answer is incorrect. The sysctl only controls stuff under /proc/sys and that does not include module parameters (even though some modules may add some additional parameters under /proc/sys). Nov 4, 2018 at 9:40

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