netdev - Re: [net-next PATCH 2/2] drivers: net: cpsw: add separate napi for tx packet handling for performance improvment

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Date:	Wed, 29 Jul 2015 10:48:56 +0530
From:	Mugunthan V N <mugunthanvnm@...com>
To:	Francois Romieu <romieu@...zoreil.com>
CC:	<netdev@...r.kernel.org>, <davem@...emloft.net>
Subject: Re: [net-next PATCH 2/2] drivers: net: cpsw: add separate napi for
 tx packet handling for performance improvment

On Wednesday 29 July 2015 04:00 AM, Francois Romieu wrote:
> Mugunthan V N <mugunthanvnm@...com> :
>> On Tuesday 28 July 2015 02:52 AM, Francois Romieu wrote:
>>> Mugunthan V N <mugunthanvnm@...com> :
> [...]
>>>> @@ -752,13 +753,22 @@ static irqreturn_t cpsw_tx_interrupt(int irq, void *dev_id)
>>>>  	struct cpsw_priv *priv = dev_id;
>>>>  
>>>>  	cpdma_ctlr_eoi(priv->dma, CPDMA_EOI_TX);
>>>> -	cpdma_chan_process(priv->txch, 128);
>>>> +	writel(0, &priv->wr_regs->tx_en);
>>>> +
>>>> +	if (netif_running(priv->ndev)) {
>>>> +		napi_schedule(&priv->napi_tx);
>>>> +		return IRQ_HANDLED;
>>>> +	}
>>>
>>>
>>> cpsw_ndo_stop calls napi_disable: you can remove netif_running.
>>>
>>
>> This netif_running check is to find which interface is up as the
>> interrupt is shared by both the interfaces. When first interface is down
>> and second interface is active then napi_schedule for first interface
>> will fail and second interface napi needs to be scheduled.
>>
>> So I don't think netif_running needs to be removed.
> 
> Each interface has its own napi tx (resp. rx) context: I would had expected
> two unconditional napi_schedule per tx (resp. rx) shared irq, not one.
> 
> I'll read it again after some sleep.
> 

For each interrupt only one napi will be scheduled, when the first
interface is down then only second interface napi is scheduled in both
tx and rx irqs.

Regards
Mugunthan V N
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