On Tue, 2019-09-10 at 09:34 -0700, Jeff Kirsher wrote:
> From: Alexander Duyck <alexander.h.du...@linux.intel.com>
>
> There were a couple cases where the ITR value generated via the adaptive
> ITR scheme could exceed 126. This resulted in the value becoming either 0
> or something less than 10. Switching back and forth between a value less
> than 10 and a value greater than 10 can cause issues as certain hardware
> features such as RSC to not function well when the ITR value has dropped
> that low.
One quick thing we can add on here is:
Fixes: b4ded8327fea ("ixgbe: Update adaptive ITR algorithm")
This is likely something that we may want to backport to stable.
> Reported-by: Gregg Leventhal <glevent...@janestreet.com>
> Signed-off-by: Alexander Duyck <alexander.h.du...@linux.intel.com>
> Tested-by: Andrew Bowers <andrewx.bow...@intel.com>
> Signed-off-by: Jeff Kirsher <jeffrey.t.kirs...@intel.com>
> ---
> drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> index dc034f4e8cf6..a5398b691aa8 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> @@ -2623,7 +2623,7 @@ static void ixgbe_update_itr(struct ixgbe_q_vector
> *q_vector,
> /* 16K ints/sec to 9.2K ints/sec */
> avg_wire_size *= 15;
> avg_wire_size += 11452;
> - } else if (avg_wire_size <= 1980) {
> + } else if (avg_wire_size < 1968) {
> /* 9.2K ints/sec to 8K ints/sec */
> avg_wire_size *= 5;
> avg_wire_size += 22420;
> @@ -2656,6 +2656,8 @@ static void ixgbe_update_itr(struct ixgbe_q_vector
> *q_vector,
> case IXGBE_LINK_SPEED_2_5GB_FULL:
> case IXGBE_LINK_SPEED_1GB_FULL:
> case IXGBE_LINK_SPEED_10_FULL:
> + if (avg_wire_size > 8064)
> + avg_wire_size = 8064;
> itr += DIV_ROUND_UP(avg_wire_size,
> IXGBE_ITR_ADAPTIVE_MIN_INC * 64) *
> IXGBE_ITR_ADAPTIVE_MIN_INC;
