linux-kernel - Re: [PATCH net-next] net: ti: icssg_prueth: Add SW TX / RX Coalescing based on hrtimers

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Message-ID: <c138f315-ed9d-4c10-b9b6-e88cc3ec5e8c@ti.com>
Date: Mon, 29 Apr 2024 11:24:02 +0530
From: MD Danish Anwar <danishanwar@...com>
To: Simon Horman <horms@...nel.org>
CC: Dan Carpenter <dan.carpenter@...aro.org>,
        Heiner Kallweit
	<hkallweit1@...il.com>, Andrew Lunn <andrew@...n.ch>,
        Jan Kiszka
	<jan.kiszka@...mens.com>,
        Diogo Ivo <diogo.ivo@...mens.com>, Paolo Abeni
	<pabeni@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>, Eric Dumazet
	<edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <srk@...com>,
        Vignesh Raghavendra
	<vigneshr@...com>, <r-gunasekaran@...com>,
        Roger Quadros <rogerq@...nel.org>
Subject: Re: [PATCH net-next] net: ti: icssg_prueth: Add SW TX / RX Coalescing
 based on hrtimers



On 27/04/24 7:11 pm, Simon Horman wrote:
> On Wed, Apr 24, 2024 at 02:48:23PM +0530, MD Danish Anwar wrote:
>> Add SW IRQ coalescing based on hrtimers for RX and TX data path for ICSSG
>> driver, which can be enabled by ethtool commands:
>>
>> - RX coalescing
>>   ethtool -C eth1 rx-usecs 50
>>
>> - TX coalescing can be enabled per TX queue
>>
>>   - by default enables coalesing for TX0
>>   ethtool -C eth1 tx-usecs 50
>>   - configure TX0
>>   ethtool -Q eth0 queue_mask 1 --coalesce tx-usecs 100
>>   - configure TX1
>>   ethtool -Q eth0 queue_mask 2 --coalesce tx-usecs 100
>>   - configure TX0 and TX1
>>   ethtool -Q eth0 queue_mask 3 --coalesce tx-usecs 100 --coalesce
>> tx-usecs 100
>>
>> Minimum value for both rx-usecs and tx-usecs is 20us.
>>
>> Comapared to gro_flush_timeout and napi_defer_hard_irqs this patch
> 
> nit: Compared
> 
>> allows to enable IRQ coalescing for RX path separately.
>>
>> Signed-off-by: MD Danish Anwar <danishanwar@...com>
> 
> ...
> 
>> @@ -190,19 +191,35 @@ int emac_tx_complete_packets(struct prueth_emac *emac, int chn,
>>  	return num_tx;
>>  }
>>  
>> +static enum hrtimer_restart emac_tx_timer_callback(struct hrtimer *timer)
>> +{
>> +	struct prueth_tx_chn *tx_chns =
>> +			container_of(timer, struct prueth_tx_chn, tx_hrtimer);
>> +
>> +	enable_irq(tx_chns->irq);
>> +	return HRTIMER_NORESTART;
>> +}
>> +
>>  static int emac_napi_tx_poll(struct napi_struct *napi_tx, int budget)
>>  {
>>  	struct prueth_tx_chn *tx_chn = prueth_napi_to_tx_chn(napi_tx);
>>  	struct prueth_emac *emac = tx_chn->emac;
>> +	bool tdown = false;
>>  	int num_tx_packets;
>>  
>> -	num_tx_packets = emac_tx_complete_packets(emac, tx_chn->id, budget);
>> +	num_tx_packets = emac_tx_complete_packets(emac, tx_chn->id, budget, &tdown);
> 
> Please consider limiting lines to 80 columns wide in Networking code.
> 
>>  
>>  	if (num_tx_packets >= budget)
>>  		return budget;
>>  
>> -	if (napi_complete_done(napi_tx, num_tx_packets))
>> -		enable_irq(tx_chn->irq);
>> +	if (napi_complete_done(napi_tx, num_tx_packets)) {
>> +		if (unlikely(tx_chn->tx_pace_timeout_ns && !tdown))
>> +			hrtimer_start(&tx_chn->tx_hrtimer,
>> +				      ns_to_ktime(tx_chn->tx_pace_timeout_ns),
>> +				      HRTIMER_MODE_REL_PINNED);
>> +		else
>> +			enable_irq(tx_chn->irq);
>> +	}
>>  
>>  	return num_tx_packets;
>>  }
> 
> ...
> 
>> @@ -870,7 +889,12 @@ int emac_napi_rx_poll(struct napi_struct *napi_rx, int budget)
>>  	}
>>  
>>  	if (num_rx < budget && napi_complete_done(napi_rx, num_rx))
>> -		enable_irq(emac->rx_chns.irq[rx_flow]);
>> +		if (unlikely(emac->rx_pace_timeout_ns))
>> +			hrtimer_start(&emac->rx_hrtimer,
>> +				      ns_to_ktime(emac->rx_pace_timeout_ns),
>> +				      HRTIMER_MODE_REL_PINNED);
>> +		else
>> +			enable_irq(emac->rx_chns.irq[rx_flow]);
> 
> clang-18 and gcc-13 both complain about the if/else logic above.
> I think it would be best to add {} to the outer if statement.
> 
>>  
>>  	return num_rx;
>>  }
> 
> ...

Sure Simon, I'll fix all this and send v2.

-- 
Thanks and Regards,
Danish