linux-kernel - Re: [PATCH v2] sched/fair: don't push cfs

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Message-ID: <20190611141219.GD15412@pauld.bos.csb>
Date:   Tue, 11 Jun 2019 10:12:19 -0400
From:   Phil Auld <pauld@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     bsegall@...gle.com, linux-kernel@...r.kernel.org,
        Xunlei Pang <xlpang@...ux.alibaba.com>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH v2] sched/fair: don't push cfs_bandwith slack timers
 forward

On Tue, Jun 11, 2019 at 03:53:25PM +0200 Peter Zijlstra wrote:
> On Thu, Jun 06, 2019 at 10:21:01AM -0700, bsegall@...gle.com wrote:
> > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> > index efa686eeff26..60219acda94b 100644
> > --- a/kernel/sched/sched.h
> > +++ b/kernel/sched/sched.h
> > @@ -356,6 +356,7 @@ struct cfs_bandwidth {
> >  	u64			throttled_time;
> >  
> >  	bool                    distribute_running;
> > +	bool                    slack_started;
> >  #endif
> >  };
> 
> I'm thinking we can this instead? afaict both idle and period_active are
> already effecitively booleans and don't need the full 16 bits.
> 
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -338,8 +338,10 @@ struct cfs_bandwidth {
>  	u64			runtime_expires;
>  	int			expires_seq;
>  
> -	short			idle;
> -	short			period_active;
> +	u8			idle;
> +	u8			period_active;
> +	u8			distribute_running;
> +	u8			slack_started;
>  	struct hrtimer		period_timer;
>  	struct hrtimer		slack_timer;
>  	struct list_head	throttled_cfs_rq;
> @@ -348,9 +350,6 @@ struct cfs_bandwidth {
>  	int			nr_periods;
>  	int			nr_throttled;
>  	u64			throttled_time;
> -
> -	bool                    distribute_running;
> -	bool                    slack_started;
>  #endif
>  };
>  


That looks reasonable to me. 

Out of curiosity, why not bool? Is sizeof bool architecture dependent?

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