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    SubjectRe: [PATCH] Introduce jiffies_32 and related compare functions
    David Miller a écrit :
    > From: Eric Dumazet <dada1@cosmosbay.com>
    > Date: Tue, 12 Dec 2006 05:09:23 +0100
    >
    >> We definitly *like* being able to use bigger timeouts on 64bits platforms.
    >>
    >> Not that they are mandatory since the same application should run fine on
    >> 32bits kernel. But as the standard type for 'tick timestamps' is 'unsigned
    >> long', a change would be invasive.
    >>
    >> Maybe some applications are now relying on being able to
    >> sleep()/select()/poll() for periods > 30 days and only run on 64
    >> bits kernels.
    >
    > I think one possible target would be struct timer, at least
    > in theory.
    >
    > There is also a line of reasoning that says that on 64-bit
    > platforms we have some flexibility to set HZ very large, if
    > we wanted to at some point, and going to 32-bit jiffies
    > storage for some things may eliminate that kind of flexibility.
    >

    Yes good point, and my understanding is that we go for a tickless kernel in
    2.6.21, or so.
    I wonder if virtual HZ wont be sticked to a low value.

    I suspect in the case HZ raises, we switch some/most uses of jiffies_32 to
    another variable (xtime_32 or whatever), but keep the storage on 32bits...

    But keeping 64bits values 'just because hardware allows us this kind of
    expenditure' seems not reasonable to me, but lazy...

    Eric

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