From: Peter Zijlstra <peterz@infradead.org>
To: Valentin Schneider <valentin.schneider@arm.com>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
riel@surriel.com
Subject: Re: [PATCH] sched: Align rq->avg_idle and rq->avg_scan_cost
Date: Mon, 30 Mar 2020 15:35:08 +0200 [thread overview]
Message-ID: <20200330133508.GN20696@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200330090127.16294-1-valentin.schneider@arm.com>
On Mon, Mar 30, 2020 at 10:01:27AM +0100, Valentin Schneider wrote:
>
> """
> The result of E1 >> E2 is E1 right-shifted E2 bit positions. [...] If E1
> has a signed type and a negative value, the resulting value is
> implementation-defined.
True; but the kernel uses -fwrapv, which would mandate 2s complement,
which then gets us to the next point:
> """
>
> Not only this, but (arithmetic) right shifting a negative value (using 2's
> complement) is *not* equivalent to dividing it by the corresponding power
> of 2.
True; good catch.
next prev parent reply other threads:[~2020-03-30 13:35 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-30 9:01 [PATCH] sched: Align rq->avg_idle and rq->avg_scan_cost Valentin Schneider
2020-03-30 13:35 ` Peter Zijlstra [this message]
2020-04-08 12:20 ` [tip: sched/urgent] sched/fair: " tip-bot2 for Valentin Schneider
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