linux-kernel - Re: [PATCH] sched/fair: Rate limit calls to update_blocked

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Message-ID: <20210512135955.suzvxxfilvwg33y2@e107158-lin.cambridge.arm.com>
Date:   Wed, 12 May 2021 14:59:55 +0100
From:   Qais Yousef <qais.yousef@....com>
To:     Tim Chen <tim.c.chen@...ux.intel.com>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Paul McKenney <paulmck@...nel.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Dietmar Eggeman <dietmar.eggemann@....com>,
        Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Mel Gorman <mgorman@...e.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        "Uladzislau Rezki (Sony)" <urezki@...il.com>,
        Neeraj upadhyay <neeraj.iitr10@...il.com>,
        Aubrey Li <aubrey.li@...ux.intel.com>
Subject: Re: [PATCH] sched/fair: Rate limit calls to
 update_blocked_averages() for NOHZ

On 05/11/21 10:25, Tim Chen wrote:
> > update_next_balance() is only used in newidle_balance() so we could
> > modify it to  have:
> > 
> > next = max(jiffies+1, next = sd->last_balance + interval)
> 
> Is the extra assignment "next = sd->last_balance + interval" needed?
> This seems more straight forward:
> 
> next = max(jiffies+1, sd->last_balance + interval)

I haven't been following the whole conversation closely, but it's always
interesting when manipulating time in non time_*() functions.

Is this max() safe against wrapping?

Thanks

--
Qais Yousef