[Intel-wired-lan] [PATCH v2] i40e: drop useless bitmap_weight() call in i40e_set_rxfh_fields()

[Intel-wired-lan] [PATCH v2] i40e: drop useless bitmap_weight() call in i40e_set_rxfh_fields()

[Yury Norov (NVIDIA)]

bitmap_weight() is O(N) and useless here, because the following
for_each_set_bit() returns immediately in case of empty flow_pctypes.

Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
---
v1: https://lore.kernel.org/all/20251216002852.334561-1-yury.norov@gmail.com/
v2: don't drop flow_id (Aleksandr).

 .../net/ethernet/intel/i40e/i40e_ethtool.c    | 21 +++++++------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_ethtool.c b/drivers/net/ethernet/intel/i40e/i40e_ethtool.c
index f2c2646ea298..e64880b6b047 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_ethtool.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_ethtool.c
@@ -3637,6 +3637,7 @@ static int i40e_set_rxfh_fields(struct net_device *netdev,
 		   ((u64)i40e_read_rx_ctl(hw, I40E_PFQF_HENA(1)) << 32);
 	DECLARE_BITMAP(flow_pctypes, FLOW_PCTYPES_SIZE);
 	u64 i_set, i_setc;
+	u8 flow_id;
 
 	bitmap_zero(flow_pctypes, FLOW_PCTYPES_SIZE);
 
@@ -3720,20 +3721,14 @@ static int i40e_set_rxfh_fields(struct net_device *netdev,
 		return -EINVAL;
 	}
 
-	if (bitmap_weight(flow_pctypes, FLOW_PCTYPES_SIZE)) {
-		u8 flow_id;
+	for_each_set_bit(flow_id, flow_pctypes, FLOW_PCTYPES_SIZE) {
+		i_setc = (u64)i40e_read_rx_ctl(hw, I40E_GLQF_HASH_INSET(0, flow_id)) |
+			 ((u64)i40e_read_rx_ctl(hw, I40E_GLQF_HASH_INSET(1, flow_id)) << 32);
+		i_set = i40e_get_rss_hash_bits(&pf->hw, nfc, i_setc);
 
-		for_each_set_bit(flow_id, flow_pctypes, FLOW_PCTYPES_SIZE) {
-			i_setc = (u64)i40e_read_rx_ctl(hw, I40E_GLQF_HASH_INSET(0, flow_id)) |
-				 ((u64)i40e_read_rx_ctl(hw, I40E_GLQF_HASH_INSET(1, flow_id)) << 32);
-			i_set = i40e_get_rss_hash_bits(&pf->hw, nfc, i_setc);
-
-			i40e_write_rx_ctl(hw, I40E_GLQF_HASH_INSET(0, flow_id),
-					  (u32)i_set);
-			i40e_write_rx_ctl(hw, I40E_GLQF_HASH_INSET(1, flow_id),
-					  (u32)(i_set >> 32));
-			hena |= BIT_ULL(flow_id);
-		}
+		i40e_write_rx_ctl(hw, I40E_GLQF_HASH_INSET(0, flow_id), (u32)i_set);
+		i40e_write_rx_ctl(hw, I40E_GLQF_HASH_INSET(1, flow_id), (u32)(i_set >> 32));
+		hena |= BIT_ULL(flow_id);
 	}
 
 	i40e_write_rx_ctl(hw, I40E_PFQF_HENA(0), (u32)hena);
-- 
2.43.0

Re: [Intel-wired-lan] [PATCH v2] i40e: drop useless bitmap_weight() call in i40e_set_rxfh_fields()

[Simon Horman]

On Wed, Dec 17, 2025 at 08:57:57PM -0500, Yury Norov (NVIDIA) wrote:
> bitmap_weight() is O(N) and useless here, because the following
> for_each_set_bit() returns immediately in case of empty flow_pctypes.
> 
> Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
> ---
> v1: https://lore.kernel.org/all/20251216002852.334561-1-yury.norov@gmail.com/
> v2: don't drop flow_id (Aleksandr).

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [Intel-wired-lan] [PATCH v2] i40e: drop useless bitmap_weight() call in i40e_set_rxfh_fields()

[Rinitha, SX]

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@osuosl.org> On Behalf Of Yury Norov (NVIDIA)
> Sent: 18 December 2025 07:28
> To: Nguyen, Anthony L <anthony.l.nguyen@intel.com>; Kitszel, Przemyslaw <przemyslaw.kitszel@intel.com>; Andrew Lunn <andrew+netdev@lunn.ch>; David S. Miller <davem@davemloft.net>; Eric Dumazet <edumazet@google.com>; Jakub Kicinski <kuba@kernel.org>; Paolo Abeni <pabeni@redhat.com>; intel-wired-lan@lists.osuosl.org; netdev@vger.kernel.org; linux-kernel@vger.kernel.org
> Cc: Yury Norov (NVIDIA) <yury.norov@gmail.com>; Loktionov, Aleksandr <aleksandr.loktionov@intel.com>
> Subject: [Intel-wired-lan] [PATCH v2] i40e: drop useless bitmap_weight() call in i40e_set_rxfh_fields()
>
> bitmap_weight() is O(N) and useless here, because the following
> for_each_set_bit() returns immediately in case of empty flow_pctypes.
>
> Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
> ---
> v1: https://lore.kernel.org/all/20251216002852.334561-1-yury.norov@gmail.com/
> v2: don't drop flow_id (Aleksandr).
>
> .../net/ethernet/intel/i40e/i40e_ethtool.c    | 21 +++++++------------
> 1 file changed, 8 insertions(+), 13 deletions(-)
>

Tested-by: Rinitha S <sx.rinitha@intel.com> (A Contingent worker at Intel)