Re: [PATCH FIX net v2] net-e1000(e): Fix default interrupt throttle rate not set in NIC HW

[Jeff Kirsher <jeffrey.t.kirsher@intel.com>]

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On Wed, 2011-11-16 at 17:46 -0800, David Decotigny wrote:
> From: Ying Cai <ycai@google.com>
> 
> This change ensures that the itr/itr_setting adjustment logic is used,
> even for the default/compiled-in value.
> 
> Context:
>   When we changed the default InterruptThrottleRate value from default
>   (3 = dynamic mode) to 8000 for example, only adapter->itr_setting
>   (which controls interrupt coalescing mode) was set to 8000, but
>   adapter->itr (which controls the value set in NIC register) was not
>   updated accordingly. So from ethtool, it seemed the interrupt
>   throttling is enabled at 8000 intr/s, but the NIC actually was
>   running in dynamic mode which has lower CPU efficiency especially
>   when throughput is not high.
> 
> 
> 
> Signed-off-by: David Decotigny <david.decotigny@google.com>
> ---
>  drivers/net/ethernet/intel/e1000/e1000_param.c |   81 +++++++++++--------
>  drivers/net/ethernet/intel/e1000e/param.c      |   98 +++++++++++++-----------
>  2 files changed, 99 insertions(+), 80 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/e1000/e1000_param.c b/drivers/net/ethernet/intel/e1000/e1000_param.c
> index 1301eba..595e462 100644
> --- a/drivers/net/ethernet/intel/e1000/e1000_param.c
> +++ b/drivers/net/ethernet/intel/e1000/e1000_param.c
> @@ -173,7 +173,7 @@ E1000_PARAM(RxAbsIntDelay, "Receive Absolute Interrupt Delay");
>  
>  /* Interrupt Throttle Rate (interrupts/sec)
>   *
> - * Valid Range: 100-100000 (0=off, 1=dynamic, 3=dynamic conservative)
> + * Valid Range: 100-100000 or one of: 0=off, 1=dynamic, 3=dynamic conservative
>   */
>  E1000_PARAM(InterruptThrottleRate, "Interrupt Throttling Rate");
>  #define DEFAULT_ITR                    3
> @@ -460,41 +460,54 @@ void __devinit e1000_check_options(struct e1000_adapter *adapter)
>  		};
>  
>  		if (num_InterruptThrottleRate > bd) {
> -			adapter->itr = InterruptThrottleRate[bd];
> -			switch (adapter->itr) {
> -			case 0:
> -				e_dev_info("%s turned off\n", opt.name);
> -				break;
> -			case 1:
> -				e_dev_info("%s set to dynamic mode\n",
> -					   opt.name);
> -				adapter->itr_setting = adapter->itr;
> -				adapter->itr = 20000;
> -				break;
> -			case 3:
> -				e_dev_info("%s set to dynamic conservative "
> -					   "mode\n", opt.name);
> -				adapter->itr_setting = adapter->itr;
> -				adapter->itr = 20000;
> -				break;
> -			case 4:
> -				e_dev_info("%s set to simplified "
> -				           "(2000-8000) ints mode\n", opt.name);
> -				adapter->itr_setting = adapter->itr;
> -				break;
> -			default:
> -				e1000_validate_option(&adapter->itr, &opt,
> -				        adapter);
> -				/* save the setting, because the dynamic bits
> -				 * change itr.
> -				 * clear the lower two bits because they are
> -				 * used as control */
> -				adapter->itr_setting = adapter->itr & ~3;
> -				break;
> -			}
> +			/* Make sure a message is printed for
> +			 * non-special values. And in case of an
> +			 * invalid option, display warning, use
> +			 * default and go through itr/itr_setting
> +			 * adjustment logic below */
> +			if ((adapter->itr < 0 || adapter->itr > 4)
> +			    && e1000_validate_option(&adapter->itr, &opt,
> +						     adapter))
> +				adapter->itr = opt.def;
>  		} else {
> -			adapter->itr_setting = opt.def;
> +			/* if no option specified, use default value
> +			   and go through the logic below to adjust
> +			   itr/itr_setting */
> +			adapter->itr = opt.def;
> +
> +			/* Make sure a message is printed for
> +			 * non-special default values */
> +			if (adapter->itr < 0 || adapter->itr > 4)
> +				e_dev_info("%s set to default %d\n",
> +					   opt.name, adapter->itr);
> +		}
> +
> +		adapter->itr_setting = adapter->itr;
> +		switch (adapter->itr) {
> +		case 0:
> +			e_dev_info("%s turned off\n", opt.name);
> +			break;
> +		case 1:
> +			e_dev_info("%s set to dynamic mode\n",
> +				   opt.name);
> +			adapter->itr = 20000;
> +			break;
> +		case 3:
> +			e_dev_info("%s set to dynamic conservative "
> +				   "mode\n", opt.name);
>  			adapter->itr = 20000;
> +			break;
> +		case 4:
> +			e_dev_info("%s set to simplified "
> +				   "(2000-8000) ints mode\n", opt.name);
> +			break;
> +		default:
> +			/* save the setting, because the dynamic bits
> +			 * change itr.
> +			 * clear the lower two bits because they are
> +			 * used as control */
> +			adapter->itr_setting &= ~3;
> +			break;
>  		}
>  	}
>  	{ /* Smart Power Down */
> diff --git a/drivers/net/ethernet/intel/e1000e/param.c b/drivers/net/ethernet/intel/e1000e/param.c
> index 20e93b0..41937e5 100644
> --- a/drivers/net/ethernet/intel/e1000e/param.c
> +++ b/drivers/net/ethernet/intel/e1000e/param.c
> @@ -106,7 +106,7 @@ E1000_PARAM(RxAbsIntDelay, "Receive Absolute Interrupt Delay");
>  /*
>   * Interrupt Throttle Rate (interrupts/sec)
>   *
> - * Valid Range: 100-100000 (0=off, 1=dynamic, 3=dynamic conservative)
> + * Valid Range: 100-100000 or one of: 0=off, 1=dynamic, 3=dynamic conservative
>   */
>  E1000_PARAM(InterruptThrottleRate, "Interrupt Throttling Rate");
>  #define DEFAULT_ITR 3
> @@ -335,53 +335,59 @@ void __devinit e1000e_check_options(struct e1000_adapter *adapter)
>  
>  		if (num_InterruptThrottleRate > bd) {
>  			adapter->itr = InterruptThrottleRate[bd];
> -			switch (adapter->itr) {
> -			case 0:
> -				e_info("%s turned off\n", opt.name);
> -				break;
> -			case 1:
> -				e_info("%s set to dynamic mode\n", opt.name);
> -				adapter->itr_setting = adapter->itr;
> -				adapter->itr = 20000;
> -				break;
> -			case 3:
> -				e_info("%s set to dynamic conservative mode\n",
> -					opt.name);
> -				adapter->itr_setting = adapter->itr;
> -				adapter->itr = 20000;
> -				break;
> -			case 4:
> -				e_info("%s set to simplified (2000-8000 ints) "
> -				       "mode\n", opt.name);
> -				adapter->itr_setting = 4;
> -				break;
> -			default:
> -				/*
> -				 * Save the setting, because the dynamic bits
> -				 * change itr.
> -				 */
> -				if (e1000_validate_option(&adapter->itr, &opt,
> -							  adapter) &&
> -				    (adapter->itr == 3)) {
> -					/*
> -					 * In case of invalid user value,
> -					 * default to conservative mode.
> -					 */
> -					adapter->itr_setting = adapter->itr;
> -					adapter->itr = 20000;
> -				} else {
> -					/*
> -					 * Clear the lower two bits because
> -					 * they are used as control.
> -					 */
> -					adapter->itr_setting =
> -						adapter->itr & ~3;
> -				}
> -				break;
> -			}
> +
> +			/* Make sure a message is printed for
> +			 * non-special values. And in case of an
> +			 * invalid option, display warning, use
> +			 * default and go through itr/itr_setting
> +			 * adjustment logic below */
> +			if ((adapter->itr < 0 || adapter->itr > 4)
> +			    && e1000_validate_option(&adapter->itr, &opt,
> +						     adapter))
> +				adapter->itr = opt.def;
>  		} else {
> -			adapter->itr_setting = opt.def;
> +			/* if no option specified, use default value
> +			   and go through the logic below to adjust
> +			   itr/itr_setting */
> +			adapter->itr = opt.def;
> +
> +			/* Make sure a message is printed for
> +			 * non-special default values */
> +			if (adapter->itr < 0 || adapter->itr > 4)
> +				e_info("%s set to default %d\n",
> +				       opt.name, adapter->itr);
> +		}
> +
> +
> +
> +		adapter->itr_setting = adapter->itr;
> +		switch (adapter->itr) {
> +		case 0:
> +			e_info("%s turned off\n", opt.name);
> +			break;
> +		case 1:
> +			e_info("%s set to dynamic mode\n", opt.name);
> +			adapter->itr = 20000;
> +			break;
> +		case 3:
> +			e_info("%s set to dynamic conservative mode\n",
> +			       opt.name);
>  			adapter->itr = 20000;
> +			break;
> +		case 4:
> +			e_info("%s set to simplified (2000-8000 ints) "
> +			       "mode\n", opt.name);
> +			break;
> +		default:
> +			/*
> +			 * Save the setting, because the dynamic bits
> +			 * change itr.
> +			 *
> +			 * Clear the lower two bits because
> +			 * they are used as control.
> +			 */
> +			adapter->itr_setting &= ~3;
> +			break;
>  		}
>  	}
>  	{ /* Interrupt Mode */

Thanks David, I have added this to my e1000e queue of patches.

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