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Thread: 18.04 - What kernel boot parameter to reserve DMA memory?

  1. #1
    Join Date
    Apr 2011
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    18.04 - What kernel boot parameter to reserve DMA memory?

    Hello everyone. I've installed 18.04 on a Desktop and I've inserted an ADLINK DMA parallel I/O card.

    What kernel boot parameter(s) do I adjust in order to allocate 20Mbytes of contiguous high memory space for the DMA?


    The Linux section of the driver install guide is VERY old - circa Ubuntu 12.04. In that section it says:

    "To prevent reduced data transfer performance caused by memory fragment, the PCIS-DASK allocates physically contigu-
    ous buffers in device driver at system startup time. For contiguous memory allocation, we reserve memory in the upper memory space.
    Users need to pass a command line argument to the kernel."

    They go on to show how it's done if you use GRUB as your bootloader. But it's ancient. For example
    they talk about editing /etc/grub.conf and adding a "mem=" statement to the grub.conf file.
    For example add mem=60M .

    But I do not have an /etc/grub.conf file. I do see the /etc/grub.d directory and I see the files underneath.

    I do see this web page which tells me how to modify/add/update kernel boot parameters:

    https://wiki.ubuntu.com/Kernel/KernelBootParameters

    But web searches on available boot parameters do not include "mem="

    Any help would be greatly appreciated.
    Last edited by saville; 3 Weeks Ago at 08:59 PM.

  2. #2
    Join Date
    Mar 2007
    Location
    Promiseland
    Beans
    925
    Distro
    Xubuntu Development Release

    Re: 18.04 - What kernel boot parameter to reserve DMA memory?

    Re: https://www.gnu.org/software/grub/manual/grub/grub.html
    16.3.77 uppermem
    This command is not yet implemented for GRUB 2, although it is planned.
    Cheers,
    I am not an expert on anything, but I pretend to be one at times.
    Software expands to consume available system resources.

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