linux-kernel - Re: [Patch v2 3/3] net: Restrict receive packets queuing to housekeeping CPUs

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Message-ID: <20200623092312.GC4781@hirez.programming.kicks-ass.net>
Date:   Tue, 23 Jun 2020 11:23:12 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Nitesh Narayan Lal <nitesh@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        frederic@...nel.org, mtosatti@...hat.com, juri.lelli@...hat.com,
        abelits@...vell.com, bhelgaas@...gle.com,
        linux-pci@...r.kernel.org, rostedt@...dmis.org, mingo@...nel.org,
        tglx@...utronix.de, davem@...emloft.net, akpm@...ux-foundation.org,
        sfr@...b.auug.org.au, stephen@...workplumber.org,
        rppt@...ux.vnet.ibm.com
Subject: Re: [Patch v2 3/3] net: Restrict receive packets queuing to
 housekeeping CPUs

On Mon, Jun 22, 2020 at 07:45:10PM -0400, Nitesh Narayan Lal wrote:
> @@ -756,6 +757,13 @@ static ssize_t store_rps_map(struct netdev_rx_queue *queue,
>  		return err;
>  	}
>  
> +	hk_flags = HK_FLAG_DOMAIN | HK_FLAG_WQ;
> +	cpumask_and(mask, mask, housekeeping_cpumask(hk_flags));
> +	if (cpumask_weight(mask) == 0) {

We have cpumask_empty() for that, which is a much more efficient way of
testing the same.

> +		free_cpumask_var(mask);
> +		return -EINVAL;
> +	}
> +
>  	map = kzalloc(max_t(unsigned int,
>  			    RPS_MAP_SIZE(cpumask_weight(mask)), L1_CACHE_BYTES),
>  		      GFP_KERNEL);
> -- 
> 2.18.4
>