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Re: [PATCH] sched/fair: fix calc_cfs_shares fixed point arithmetics

From Samuel Thibault <samuel.thibault@ens-lyon.org>
Newsgroups linux.kernel
Subject Re: [PATCH] sched/fair: fix calc_cfs_shares fixed point arithmetics
Date 2016-12-20 00:40 +0100
Message-ID <sQfHb-605-5@gated-at.bofh.it> (permalink)
References <sQeUN-5sP-13@gated-at.bofh.it> <sQeUN-5sP-11@gated-at.bofh.it> <sQfea-5OT-11@gated-at.bofh.it> <sQfxw-5WR-29@gated-at.bofh.it>
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Paul Turner, on Mon 19 Dec 2016 15:26:19 -0800, wrote:
> >> > -       if (shares < MIN_SHARES)
> >> > -               shares = MIN_SHARES;
> > ...
> >> >         return shares;
> >
> > This will only make sure that the returned shares is 2, not 2048.
> 
> This is intentional.  The MIN_SHARES you are seeing here is overloaded.
> Every "1" unit of share is "SCHED_LOAD_RESOLUTION" bits internally.

I'm not talking about the SCHED_LOAD_RESOLUTION scaling, but about the
SCHED_FIXEDPOINT_SHIFT scaling, which is what
2159197d6677 ("sched/core: Enable increased load resolution on 64-bit kernels")
modified on 64bit platforms.

Samuel

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Re: [PATCH] sched/fair: fix calc_cfs_shares fixed point arithmetics Paul Turner <pjt@kernel.org> - 2016-12-19 23:50 +0100
  Re: [PATCH] sched/fair: fix calc_cfs_shares fixed point arithmetics Samuel Thibault <samuel.thibault@ens-lyon.org> - 2016-12-20 00:10 +0100
    Re: [PATCH] sched/fair: fix calc_cfs_shares fixed point arithmetics Paul Turner <pjt@kernel.org> - 2016-12-20 00:30 +0100
      Re: [PATCH] sched/fair: fix calc_cfs_shares fixed point arithmetics Samuel Thibault <samuel.thibault@ens-lyon.org> - 2016-12-20 00:40 +0100
        Re: [PATCH] sched/fair: fix calc_cfs_shares fixed point arithmetics Paul Turner <pjt@kernel.org> - 2016-12-20 00:40 +0100
          Re: [PATCH] sched/fair: fix calc_cfs_shares fixed point arithmetics Samuel Thibault <samuel.thibault@ens-lyon.org> - 2016-12-20 00:50 +0100
            Re: [PATCH] sched/fair: fix calc_cfs_shares fixed point arithmetics Dietmar Eggemann <dietmar.eggemann@arm.com> - 2016-12-20 14:10 +0100
              Re: [PATCH] sched/fair: fix calc_cfs_shares fixed point arithmetics Peter Zijlstra <peterz@infradead.org> - 2016-12-20 14:20 +0100
              Re: [PATCH] sched/fair: fix calc_cfs_shares fixed point arithmetics Samuel Thibault <samuel.thibault@ens-lyon.org> - 2016-12-20 14:30 +0100

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