linux-kernel - Re: [BUG] 3.19-rc1 net: less interrupt masking in NAPI

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Date:	Sun, 11 Jan 2015 00:08:52 +0200
From:	Oded Gabbay <oded.gabbay@....com>
To:	Eric Dumazet <eric.dumazet@...il.com>,
	Johannes Berg <johannes.berg@...el.com>
CC:	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Willem de Bruijn <willemb@...gle.com>,
	"Bridgman, John" <John.Bridgman@....com>,
	"Elifaz, Dana" <Dana.Elifaz@....com>
Subject: Re: [BUG] 3.19-rc1 net: less interrupt masking in NAPI



On 01/11/2015 12:05 AM, Oded Gabbay wrote:
> 
> 
> On 01/10/2015 11:50 PM, Eric Dumazet wrote:
>> On Sat, 2015-01-10 at 23:30 +0200, Oded Gabbay wrote:
>>
>>> Yes, no problem.
>>> I will update on the result.
>>
>> Please try this more complete patch, solving the TX pressure problem as
>> well, and not lying about NAPI budget. thanks !
>>
>>
>> diff --git a/drivers/net/ethernet/atheros/alx/main.c b/drivers/net/ethernet/atheros/alx/main.c
>> index e398eda07298..5f05b387c0a7 100644
>> --- a/drivers/net/ethernet/atheros/alx/main.c
>> +++ b/drivers/net/ethernet/atheros/alx/main.c
>> @@ -184,15 +184,16 @@ static void alx_schedule_reset(struct alx_priv *alx)
>>  	schedule_work(&alx->reset_wk);
>>  }
>>  
>> -static bool alx_clean_rx_irq(struct alx_priv *alx, int budget)
>> +static int alx_clean_rx_irq(struct alx_priv *alx, int budget)
>>  {
>>  	struct alx_rx_queue *rxq = &alx->rxq;
>>  	struct alx_rrd *rrd;
>>  	struct alx_buffer *rxb;
>>  	struct sk_buff *skb;
>>  	u16 length, rfd_cleaned = 0;
>> +	int work = 0;
>>  
>> -	while (budget > 0) {
>> +	while (work < budget) {
>>  		rrd = &rxq->rrd[rxq->rrd_read_idx];
>>  		if (!(rrd->word3 & cpu_to_le32(1 << RRD_UPDATED_SHIFT)))
>>  			break;
>> @@ -243,7 +244,7 @@ static bool alx_clean_rx_irq(struct alx_priv *alx, int budget)
>>  		}
>>  
>>  		napi_gro_receive(&alx->napi, skb);
>> -		budget--;
>> +		work++;
>>  
>>  next_pkt:
>>  		if (++rxq->read_idx == alx->rx_ringsz)
>> @@ -258,21 +259,22 @@ next_pkt:
>>  	if (rfd_cleaned)
>>  		alx_refill_rx_ring(alx, GFP_ATOMIC);
>>  
>> -	return budget > 0;
>> +	return work;
>>  }
>>  
>>  static int alx_poll(struct napi_struct *napi, int budget)
>>  {
>>  	struct alx_priv *alx = container_of(napi, struct alx_priv, napi);
>>  	struct alx_hw *hw = &alx->hw;
>> -	bool complete = true;
>>  	unsigned long flags;
>> +	bool tx_complete;
>> +	int work;
>>  
>> -	complete = alx_clean_tx_irq(alx) &&
>> -		   alx_clean_rx_irq(alx, budget);
>> +	tx_complete = alx_clean_tx_irq(alx);
>> +	work = alx_clean_rx_irq(alx, budget);
>>  
>> -	if (!complete)
>> -		return 1;
>> +	if (!tx_complete || work == budget)
>> +		return budget;
>>  
>>  	napi_complete(&alx->napi);
>>  
>> @@ -284,7 +286,7 @@ static int alx_poll(struct napi_struct *napi, int budget)
>>  
>>  	alx_post_write(hw);
>>  
>> -	return 0;
>> +	return work;
>>  }
>>  
>>  static irqreturn_t alx_intr_handle(struct alx_priv *alx, u32 intr)
>>
>>
> Hi,
> Checked it and its working.
> Thanks again.
> Please note that I only use this Ethernet controller for NFS and SCP, it is
> not used for development of networking software of any kind, so maybe a more
> extensive testing is needed.
> 
> 	Oded
> --
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> 

But in any case, you can add:
Tested-by: Oded Gabbay <oded.gabbay@....com>

	Oded
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