From: Peter Zijlstra <peterz@infradead.org>
To: Chunyan Zhang <chunyan.zhang@unisoc.com>
Cc: Ingo Molnar <mingo@redhat.com>,
Vincent Wang <vincent.wang@unisoc.com>,
Quentin Perret <quentin.perret@arm.com>,
linux-kernel@vger.kernel.org,
Chunyan Zhang <zhang.lyra@gmail.com>
Subject: Re: [PATCH V2] sched/cpufreq: calculate util / cap in advance in map_util_freq()
Date: Fri, 18 Jan 2019 17:16:16 +0100 [thread overview]
Message-ID: <20190118161616.GH14054@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <1547089325-15691-1-git-send-email-chunyan.zhang@unisoc.com>
On Thu, Jan 10, 2019 at 11:02:05AM +0800, Chunyan Zhang wrote:
> From: Vincent Wang <vincent.wang@unisoc.com>
>
> When a task that is in_iowait state is enqueued, cpufreq_update_util()
> will be invoked with SCHED_CPUFREQ_IOWAIT flag. In this case,the value
> of util and cap, which are parameters used in map_util_freq(), will be
> cpu frequency, instead of cpu util and capactiy.
>
> For some 32bit architectures, the size of unsigned long is 32. When
> calculating freq, there may be an overflow error in this expression:
Would it not be much better to fix that one case instead of adding extra
instructions for everyone all the time?
prev parent reply other threads:[~2019-01-18 16:16 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-10 3:02 Chunyan Zhang
2019-01-18 16:16 ` Peter Zijlstra [this message]
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