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 00:30:13 +0200
From:	Francois Romieu <romieu@...zoreil.com>
To:	Mugunthan V N <mugunthanvnm@...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

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.

-- 
Ueimor
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