From: Samuel Thibault <samuel.thibault@ens-lyon.org>
To: Paul Turner <pjt@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH] sched/fair: fix calc_cfs_shares fixed point arithmetics
Date: Tue, 20 Dec 2016 00:29:26 +0100 [thread overview]
Message-ID: <20161219232926.GH2895@var.home> (raw)
In-Reply-To: <CAPM31RKZkrT=6mg=eeBCVmwY7Put-Pu+46Osw_TR56YXz-+esg@mail.gmail.com>
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
next prev parent reply other threads:[~2016-12-19 23:29 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-19 22:40 Samuel Thibault
2016-12-19 22:44 ` Paul Turner
2016-12-19 23:07 ` Samuel Thibault
2016-12-19 23:26 ` Paul Turner
2016-12-19 23:29 ` Samuel Thibault [this message]
2016-12-19 23:32 ` Paul Turner
2016-12-19 23:45 ` Samuel Thibault
2016-12-20 13:04 ` Dietmar Eggemann
2016-12-20 13:15 ` Peter Zijlstra
2017-01-11 11:29 ` Dietmar Eggemann
2017-01-14 12:48 ` [tip:sched/core] sched/fair: Explain why MIN_SHARES isn't scaled in calc_cfs_shares() tip-bot for Dietmar Eggemann
2016-12-20 13:22 ` [PATCH] sched/fair: fix calc_cfs_shares fixed point arithmetics Samuel Thibault
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