linux-kernel - Re: [PATCH v2] sched/isolation: add a workqueue parameter to constrain unbound CPUs

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Date:   Wed, 21 Jun 2023 10:51:26 -1000
From:   Tejun Heo <tj@...nel.org>
To:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.co,
        vincent.guittot@...aro.org, linux-kernel@...r.kernel.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, vschneid@...hat.com,
        fuyuanli@...iglobal.com, zwp10758@...il.com, zyhtheonly@...il.com,
        zyhtheonly@...h.net
Subject: Re: [PATCH v2] sched/isolation: add a workqueue parameter to
 constrain unbound CPUs

On Wed, Jun 14, 2023 at 05:19:45PM +0800, tiozhang wrote:
...
> @@ -181,8 +181,8 @@ static int __init housekeeping_nohz_full_setup(char *str)
>  {
>  	unsigned long flags;
>  
> -	flags = HK_FLAG_TICK | HK_FLAG_WQ | HK_FLAG_TIMER | HK_FLAG_RCU |
> -		HK_FLAG_MISC | HK_FLAG_KTHREAD;
> +	flags = HK_FLAG_TICK | HK_FLAG_TIMER | HK_FLAG_RCU | HK_FLAG_MISC
> +		| HK_FLAG_KTHREAD;

Why is WQ being taken out of nohz_full setup? The patch description doesn't
mention anything.

> @@ -208,6 +208,12 @@ static int __init housekeeping_isolcpus_setup(char *str)
>  			continue;
>  		}
>  
> +		if (!strncmp(str, "workqueue,", 10)) {
> +			str += 10;
> +			flags |= HK_FLAG_WQ;
> +			continue;
> +		}

I wonder whether it'd be better to just add a workqueue boot param but if
this works it's fine too.

Thanks.

-- 
tejun