netdev - Re: [PATCH net-next 1/9] net: better skb->sender_cpu and skb->napi

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Message-ID: <20151117174234.GB89026@ast-mbp.thefacebook.com>
Date:	Tue, 17 Nov 2015 09:42:34 -0800
From:	Alexei Starovoitov <alexei.starovoitov@...il.com>
To:	Eric Dumazet <edumazet@...gle.com>
Cc:	"David S . Miller" <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>, Eli Cohen <eli@...lanox.com>,
	Amir Vadai <amirv@...lanox.com>,
	Ariel Elior <ariel.elior@...gic.com>,
	Willem de Bruijn <willemb@...gle.com>,
	Rida Assaf <rida@...gle.com>,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH net-next 1/9] net: better skb->sender_cpu and
 skb->napi_id cohabitation

On Tue, Nov 17, 2015 at 05:56:56AM -0800, Eric Dumazet wrote:
> skb->sender_cpu and skb->napi_id share a common storage,
> and we had various bugs about this.
> 
> We had to call skb_sender_cpu_clear() in some places to
> not leave a prior skb->napi_id and fool netdev_pick_tx()
> 
> As suggested by Alexei, we could split the space so that
> these errors can not happen.
> 
> 0 value being reserved as the common (not initialized) value,
> let's reserve [1 .. NR_CPUS] range for valid sender_cpu,
> and [NR_CPUS+1 .. ~0U] for valid napi_id.

nice. that's a cleaner and simpler range split.

> This will allow proper busy polling support over tunnels.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Suggested-by: Alexei Starovoitov <ast@...nel.org>

Acked-by: Alexei Starovoitov <ast@...nel.org>

Great series of patches! Looking forward to try them out on rpc workloads.

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