On Fri, May 08, 2026 at 05:12:25AM +0200, Aleksandr Loktionov wrote: > From: Alexander Duyck <[email protected]> > > When operating in latency mode and the computed ITR is lower than the > current setting, the algorithm can reduce the interrupt rate too > aggressively in a single step. For a TCP workload this means the ACK > stream (a latency-sensitive, low-packet-rate workload) can drive the > moderation down to very high interrupt rates, starving CPU time from > the sender side. > > After the speed-based ITR calculation is complete, check whether the > result is in latency mode and would decrease below the current setting. > If so, limit the decrease to at most IXGBE_ITR_ADAPTIVE_MIN_INC (2 us) > per update. This ensures the number of interrupts grows by no more > than 2x per adjustment step for latency-class workloads, dialling in > smoothly rather than overshooting. > > Signed-off-by: Alexander Duyck <[email protected]> > Signed-off-by: Aleksandr Loktionov <[email protected]>
Reviewed-by: Simon Horman <[email protected]> > --- > drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c > b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c > index aea76b3..ba7b013 100644 > --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c > +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c > @@ -2888,6 +2888,17 @@ static void ixgbe_update_itr(struct ixgbe_q_vector > *q_vector, > break; > } > > + /* In the case of a latency specific workload only allow us to > + * reduce the ITR by at most 2us. By doing this we should dial > + * in so that our number of interrupts is no more than 2x the number > + * of packets for the least busy workload. So for example in the case > + * of a TCP workload the ACK packets being received would set the > + * interrupt rate as they are a latency specific workload. > + */ > + if ((itr & IXGBE_ITR_ADAPTIVE_LATENCY) && itr < ring_container->itr) > + itr = max_t(unsigned int, itr, > + ring_container->itr - IXGBE_ITR_ADAPTIVE_MIN_INC); nit: I expect this could be min(). And if it could, it should. > + > clear_counts: > /* write back value */ > ring_container->itr = itr; > -- > 2.52.0 >
