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    SubjectRe: [PATCH] Add Kconfig option for default swappiness
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    On Tue, 2 Nov 2010 22:01:20 +0800, Wu Fengguang <fengguang.wu@intel.com> wrote:
    > It's interesting to know what value you plan to use for your
    > desktop/server systems and the rationals (is it based on any
    > testing results?).

    This is something that will likely require a great deal of research,
    thinking, and testing. I wish I could give you a better answer at the
    moment. I have read many opinions on this but have not seen enough
    evidence to suggest specific values. In the desktop case, it seems clear
    that the preferred value should be lower than the current default to
    preserve interactive performance (long latencies due to swapping is
    something that many desktop users complain about currently). I set
    swappiness to 10 on my own machines machines with good results, but mine
    is anything but a model case. I don't believe there is any direct need
    to touch the server kernel swappiness at the moment.

    > And why it's easier to do it in kernel (hope it's not because of
    > trouble communicating with the user space packaging team).

    Fear not, this is certainly not the case. We would simply like to be
    able to keep this our kernel configuration self-contained. We already
    have separate packages for various kernel flavors with their own
    configurations. Allowing us to tune swappiness from the configuration
    would keep things much cleaner.

    The other option would be to drop a file in /etc/sysctl.d from the
    kernel meta-package (e.g. linux-image-generic and
    linux-image-server). However, it would make little sense to do this
    without adding a dependency on procps to this package (although,
    admittedly, procps is in the default installation) which we would rather
    not do if possible. Furthermore, this spreads the kernel configuration
    across the system. In sum, it seems that configuring the default in the
    kernel itself is by far the most elegant way to proceed.

    Cheers,

    - Ben


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