netdev - Re: [PATCH bpf-next v2 01/10] net: introduce preferred busy-polling

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Message-ID: <20201116080457.163bf83b@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Mon, 16 Nov 2020 08:04:57 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Björn Töpel <bjorn.topel@...il.com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        Björn Töpel 
        <bjorn.topel@...el.com>, magnus.karlsson@...el.com, ast@...nel.org,
        daniel@...earbox.net, maciej.fijalkowski@...el.com,
        sridhar.samudrala@...el.com, jesse.brandeburg@...el.com,
        qi.z.zhang@...el.com, edumazet@...gle.com,
        jonathan.lemon@...il.com, maximmi@...dia.com
Subject: Re: [PATCH bpf-next v2 01/10] net: introduce preferred busy-polling

On Mon, 16 Nov 2020 12:04:07 +0100 Björn Töpel wrote:
> @@ -6771,6 +6806,19 @@ static int napi_poll(struct napi_struct *n, struct list_head *repoll)
>  	if (likely(work < weight))
>  		goto out_unlock;
>  
> +	/* The NAPI context has more processing work, but busy-polling
> +	 * is preferred. Exit early.
> +	 */
> +	if (napi_prefer_busy_poll(n)) {
> +		if (napi_complete_done(n, work)) {
> +			/* If timeout is not set, we need to make sure
> +			 * that the NAPI is re-scheduled.
> +			 */
> +			napi_schedule(n);
> +		}
> +		goto out_unlock;
> +	}

Why is this before the disabled check?

>  	/* Drivers must not modify the NAPI state if they
>  	 * consume the entire weight.  In such cases this code
>  	 * still "owns" the NAPI instance and therefore can