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    SubjectRe: [RFC] Dynamic Tick and Deferrable Timer Support
    Pallipadi, Venkatesh wrote:

    > max_delta would depend on the timer in the platform. With HPET this
    > should be much larger than 2.15 secs.

    So I agree that the HPET hardware in newer devices themselves would
    allow longer sleep periods. However, this is not the problem I was raising.

    The problem is that the dynamic tick uses a 32-bit variable,
    max_delta_ns, to define that max sleep time of a device in nanoseconds.
    The maximum value that this variable can be assigned is LONG_MAX or
    0x7fffffff nanoseconds (see function clockevent_delta2ns). The value
    0x7fffffff nanoseconds equates to ~2.15 seconds. Hence, without
    increasing the dynamic range of max_delta_ns (ie. make this a 64-bit
    integer) or change the base of this variable from nanoseconds to
    milliseconds, I don't see how the device will ever sleep for longer than
    ~2.15 seconds.

    I have spent several weeks trying to suppress kernel timers using the
    deferred timers and lengthen the sleep time. I am now able to get the
    device to sleep for minutes but I found that max_delta_ns is a limiting
    factor. I will be surprised if you can sleep for longer than ~2.15
    seconds with the current implementation.

    Let me know if this makes sense.

    > Ok. Thinking about it a bit more, I think we can push this
    > patch along.
    > Thomas/Andrew, can one of you pick up this patch..

    Great thanks.

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      Last update: 2009-01-29 17:33    [W:0.021 / U:10.840 seconds]
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