* Re: [Intel-wired-lan] [PATCH 249/249] net:ethernet:intel:igb_main.c: Add Throttling disable option in order to decrease latency usually required by RT applications.
[not found] ` <48faffefd02040f7a2af65691454ad3c@Hummer.waves.com>
@ 2016-09-07 14:49 ` Duyck, Alexander H
0 siblings, 0 replies; 2+ messages in thread
From: Duyck, Alexander H @ 2016-09-07 14:49 UTC (permalink / raw)
To: amiry@waves.com, Kirsher, Jeffrey T
Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
intel-wired-lan@lists.osuosl.org, shannon.nelson@intel.com,
rostedt@goodmis.org, matthew.vick@intel.com,
john.ronciak@intel.com
On Tue, 2016-09-06 at 14:46 +0000, Amir Yihie wrote:
> From e433f5bedd49a65b7337d025f3f204f0f21ad5e5 Mon Sep 17 00:00:00
> 2001
> From: amiry <amiry@waves.com>
> Date: Tue, 6 Sep 2016 14:58:38 +0300
> Subject: [PATCH 249/249] net:ethernet:intel:igb_main.c: Add
> Throttling disable
> option in order to decrease latency usually required by RT
> applications.
>
> Add an option to Disable Throttling algorithm , which will result
> with minimum latency on received frames .
> mainly targets for RT application that look for low larceny and less
> cares about throughput .
> How to use :
> On insmod , add parameter : InterruptThrottleRate=0
>
> This patch is currently against a linux 4.1.27-rt31 kernel.
>
> Signed-off-by: Amir Yihie <amiry@waves.com>
> ---
> drivers/net/ethernet/intel/igb/igb_main.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c
> b/drivers/net/ethernet/intel/igb/igb_main.c
> index 7dfbcde..9480850 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -251,6 +251,14 @@ static int debug = -1;
> module_param(debug, int, 0);
> MODULE_PARM_DESC(debug, "Debug level (0=none,...,16=all)");
>
> +/* Interrupt Throttle Rate (interrupts/sec)
> + *
> + * Valid Range: 0=off, 3=dynamic conservative
> + */
> +static int InterruptThrottleRate = 3;
> +module_param(InterruptThrottleRate, int, 0);
> +MODULE_PARM_DESC(InterruptThrottleRate, "InterruptThrottleRate
> (0=off, 3=dynamic conservative)");
> +
This is creating redundant functionality. The same can be done via the
ethtool command "ethtool -C <iface> rx-usecs 0". Is there some reason
why you couldn't use ethtool?
> struct igb_reg_info {
> u32 ofs;
> char *name;
> @@ -2966,6 +2974,9 @@ static int igb_sw_init(struct igb_adapter
> *adapter)
> adapter->rx_itr_setting = IGB_DEFAULT_ITR;
> adapter->tx_itr_setting = IGB_DEFAULT_ITR;
>
> + if (InterruptThrottleRate == 0)
> + adapter->rx_itr_setting = InterruptThrottleRate;
> +
> /* set default work limits */
> adapter->tx_work_limit = IGB_DEFAULT_TX_WORK;
If you are going to use InterruptThrottleRate you might as well use it
fully instead of making it a boolean value with 0 having one meaning
and the default of 3 being another.
Thanks.
- Alex
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