[Intel-wired-lan] [PATCH] i40e: Fix RS bit update in Tx path and disable force WB workaround

[Bowers, AndrewX]

> -----Original Message-----
> From: Intel-wired-lan [mailto:intel-wired-lan-bounces at lists.osuosl.org] On
> Behalf Of Anjali Singhai Jain
> Sent: Friday, September 25, 2015 6:26 PM
> To: intel-wired-lan at lists.osuosl.org
> Subject: [Intel-wired-lan] [PATCH] i40e: Fix RS bit update in Tx path and
> disable force WB workaround
> 
> This patch fixes the issue of forcing WB too often causing us to not benefit
> from NAPI.
> 
> Without this patch we were forcing WB/arming interrupt too often taking
> away the benefits of NAPI and causing a performance impact.
> 
> With this patch we disable force WB in the clean routine for X710 and XL710
> adapters. X722 adapters do not enable interrupt to force a WB and benefit
> from WB_ON_ITR and hence force WB is left enabled for those adapters.
> For XL710 and X710 adapters if we have less than 4 packets pending a
> software Interrupt triggered from service task will force a WB.
> 
> This patch also changes the conditions for setting RS bit as described in code
> comments. This optimizes when the HW does a tail bump amd when it does a
> WB. It also optimizes when we do a wmb.
> 
> Signed-off-by: Anjali Singhai Jain <anjali.singhai at intel.com>
> ---
>  drivers/net/ethernet/intel/i40e/i40e_txrx.c | 126 ++++++++++++++++++---
> -------
>  drivers/net/ethernet/intel/i40e/i40e_txrx.h |   2 +
>  2 files changed, 86 insertions(+), 42 deletions(-)

Tested-by: Andrew Bowers <andrewx.bowers at intel.com>
Code changes present in tree