From 3a9e5fff2ab0d6f4af701757d35b9453dc563b78 Mon Sep 17 00:00:00 2001 From: Maxim Mikityanskiy Date: Tue, 25 Jan 2022 12:52:59 +0200 Subject: [PATCH] net/mlx5e: Optimize modulo in mlx5e_select_queue To improve the performance of the modulo operation (%), it's replaced by a subtracting the divisor in a loop. The modulo is used to fix up an out-of-bounds value that might be returned by netdev_pick_tx or to convert the queue number to the channel number when num_tcs > 1. Both situations are unlikely, because XPS is configured not to pick higher queues (qid >= num_channels) by default, so under normal circumstances the flow won't go inside the loop, and it will be faster than %. num_tcs == 8 adds at most 7 iterations to the loop. PTP adds at most 1 iteration to the loop. HTB would add at most 256 iterations (when num_channels == 1), so there is an additional boundary check in the HTB flow, which falls back to % if more than 7 iterations are expected. Signed-off-by: Maxim Mikityanskiy Reviewed-by: Tariq Toukan Signed-off-by: Saeed Mahameed --- .../net/ethernet/mellanox/mlx5/core/en/selq.c | 7 ++++--- .../net/ethernet/mellanox/mlx5/core/en/selq.h | 20 +++++++++++++++++++ 2 files changed, 24 insertions(+), 3 deletions(-) diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/selq.c b/drivers/net/ethernet/mellanox/mlx5/core/en/selq.c index b3ed5262d2a16..667bc95a0d44a 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/en/selq.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/en/selq.c @@ -178,7 +178,8 @@ u16 mlx5e_select_queue(struct net_device *dev, struct sk_buff *skb, * So we can return a txq_ix that matches the channel and * packet UP. */ - return txq_ix % selq->num_channels + up * selq->num_channels; + return mlx5e_txq_to_ch_ix(txq_ix, selq->num_channels) + + up * selq->num_channels; } if (unlikely(selq->is_htb)) { @@ -198,7 +199,7 @@ u16 mlx5e_select_queue(struct net_device *dev, struct sk_buff *skb, * Driver to select these queues only at mlx5e_select_ptpsq() * and mlx5e_select_htb_queue(). */ - return txq_ix % selq->num_channels; + return mlx5e_txq_to_ch_ix_htb(txq_ix, selq->num_channels); } /* PTP is enabled */ @@ -214,7 +215,7 @@ u16 mlx5e_select_queue(struct net_device *dev, struct sk_buff *skb, * If netdev_pick_tx() picks ptp_channel, switch to a regular queue, * because driver should select the PTP only at mlx5e_select_ptpsq(). */ - txq_ix %= selq->num_channels; + txq_ix = mlx5e_txq_to_ch_ix(txq_ix, selq->num_channels); if (selq->num_tcs <= 1) return txq_ix; diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/selq.h b/drivers/net/ethernet/mellanox/mlx5/core/en/selq.h index b1c73b509f6b0..6c070141d8f11 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/en/selq.h +++ b/drivers/net/ethernet/mellanox/mlx5/core/en/selq.h @@ -25,6 +25,26 @@ void mlx5e_selq_prepare(struct mlx5e_selq *selq, struct mlx5e_params *params, bo void mlx5e_selq_apply(struct mlx5e_selq *selq); void mlx5e_selq_cancel(struct mlx5e_selq *selq); +static inline u16 mlx5e_txq_to_ch_ix(u16 txq, u16 num_channels) +{ + while (unlikely(txq >= num_channels)) + txq -= num_channels; + return txq; +} + +static inline u16 mlx5e_txq_to_ch_ix_htb(u16 txq, u16 num_channels) +{ + if (unlikely(txq >= num_channels)) { + if (unlikely(txq >= num_channels << 3)) + txq %= num_channels; + else + do + txq -= num_channels; + while (txq >= num_channels); + } + return txq; +} + u16 mlx5e_select_queue(struct net_device *dev, struct sk_buff *skb, struct net_device *sb_dev); -- 2.30.2