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    SubjectRe: [PATCH 11/17] staging: lustre: libcfs: discard cfs_time_shift().
    On Mon, Apr 02 2018, Dilger, Andreas wrote:

    >> On Mar 30, 2018, at 13:02, James Simmons <jsimmons@infradead.org> wrote:
    >>
    >>
    >>> This function simply multiplies by HZ and adds jiffies.
    >>> This is simple enough to be opencoded, and doing so
    >>> makes the code easier to read.
    >>>
    >>> Same for cfs_time_shift_64()
    >>
    >> Reviewed-by: James Simmons <jsimmons@infradead.org>
    >
    > Hmm, I thought we were trying to get rid of direct HZ usage in modules,
    > because of tickless systems, and move to e.g. msecs_to_jiffies() or similar?

    Are we? I hadn't heard but I could easily have missed it.
    Documentation/scheduler/completion.txt does say

    Timeouts are preferably calculated with
    msecs_to_jiffies() or usecs_to_jiffies().

    but is isn't clear what they are preferred to. Do you remember where
    you heard? or have a reference?

    $ git grep ' \* *HZ' |wc
    2244 15679 170016
    $ git grep msecs_to_jiffies | wc
    3301 13151 276725

    so msecs_to_jiffies is slightly more popular than "* HZ" (even if you add
    in "HZ *"). But that could just be a preference for using milliseconds
    over using seconds.

    $ git grep msecs_to_jiffies | grep -c '[0-9]000'
    587

    so there are only 587 places that msecs_to_jiffies is clearly used in
    place of multiplying by HZ.

    If we were to pursue this, I would want to add secs_to_jiffies() to
    include/linux/jiffies.h and use that.

    Thanks,
    NeilBrown
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