netdev - Re: [PATCH net-next 0/2] sunvnet: Packet processing in non-interrupt context.

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Message-ID: <1412190659.16704.60.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Wed, 01 Oct 2014 12:10:59 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Sowmini Varadhan <sowmini.varadhan@...cle.com>
Cc:	davem@...emloft.net, raghuram.kothakota@...cle.com,
	netdev@...r.kernel.org
Subject: Re: [PATCH net-next 0/2] sunvnet: Packet processing in
 non-interrupt context.

On Wed, 2014-10-01 at 14:56 -0400, Sowmini Varadhan wrote:
> The existing sunvnet implementation does all the packet interception
> in LDC interrupt context. Patch 1 of this series moves the data
> processing to a bottom-half handler.
> 
> Some context for the reasons for choosing a BH handler over NAPI:
>    A NAPI (or simple tasklet) based implementation provides softirq
>    context, which allows the driver to safely invoke netif_receive_skb()
>    to deliver the packet to the IP stack. But in the case of sunvnet,
>    we are already receiving multiple packets for a single ldc_rx
>    interrupt, so the budget-based softirq-vs-polling infra does not
>    provide a significant optimization. Rather, it can get in the way,
>    if we constrain the vnet-rx path to a poorly chosen budget, and force
>    ourselves to send a STOPPED/START ldc exchange needlessly.

I do not think we can accept this.

You basically found a way to overcome NAPI standard limits (budget of
64)



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