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    SubjectRe: [PATCH v4 0/8] support for bitmap (and hence CPU) list "N" abbreviation
    On 10/02/2021 18.57, Paul E. McKenney wrote:
    > On Wed, Feb 10, 2021 at 06:26:54PM +0200, Andy Shevchenko wrote:
    >> On Tue, Feb 09, 2021 at 05:58:59PM -0500, Paul Gortmaker wrote:
    >>> The basic objective here was to add support for "nohz_full=8-N" and/or
    >>> "rcu_nocbs="4-N" -- essentially introduce "N" as a portable reference
    >>> to the last core, evaluated at boot for anything using a CPU list.
    >> I thought we kinda agreed that N is confusing and L is better.
    >> N to me is equal to 32 on 32 core system as *number of cores / CPUs*. While L
    >> sounds better as *last available CPU number*.
    > The advantage of "N" is that people will automatically recognize it as
    > "last thing" or number of things" because "N" has long been used in
    > both senses. In contrast, someone seeing "0-L" for the first time is
    > likely to go "What???".

    Completely agree. The patch that introduces this even updates
    Documentation/ at the same time, and if people are confused just because
    they don't RTFM, xkcd#293 applies. So let's please just paint the
    bikeshed N. (As for case insensitivity, I don't see the point, it just
    makes documentation and implementation more cumbersome and confusing.
    Just document and implement _one_ way of doing this.)

    As for a future syntax for "last 4 cpus", it's common to accept a
    negative index to mean count from the end, so unless we already accept
    -4 as a shorthand for 0-4 (haven't checked), that could be -4-N. But
    regardless, I also agree with Paul on this point, that's for a future
    time when the need arises.


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