netdev - [PATCH v2 net-next 2/2] net: Cache hash and flow

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250715112431.2178100-3-krikku@gmail.com>
Date: Tue, 15 Jul 2025 16:54:31 +0530
From: Krishna Kumar <krikku@...il.com>
To: netdev@...r.kernel.org,
	davem@...emloft.net,
	edumazet@...gle.com
Cc: tom@...bertland.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	horms@...nel.org,
	sdf@...ichev.me,
	kuniyu@...gle.com,
	ahmed.zaki@...el.com,
	aleksander.lobakin@...el.com,
	atenart@...nel.org,
	jdamato@...tly.com,
	krishna.ku@...pkart.com
Subject: [PATCH v2 net-next 2/2] net: Cache hash and flow_id to avoid recalculation

get_rps_cpu() can cache flow_id and hash as both are required by
set_rps_cpu() instead of recalculating them twice.

Signed-off-by: Krishna Kumar <krikku@...il.com>
---
 net/core/dev.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index d6eece960d0d..09b989aa9ef0 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4861,7 +4861,8 @@ static bool rps_flow_is_active(struct rps_dev_flow *rflow,
 
 static struct rps_dev_flow *
 set_rps_cpu(struct net_device *dev, struct sk_buff *skb,
-	    struct rps_dev_flow *rflow, u16 next_cpu)
+	    struct rps_dev_flow *rflow, u16 next_cpu, u32 hash,
+	    u32 flow_id)
 {
 	if (next_cpu < nr_cpu_ids) {
 		u32 head;
@@ -4872,8 +4873,6 @@ set_rps_cpu(struct net_device *dev, struct sk_buff *skb,
 		struct rps_dev_flow *tmp_rflow;
 		unsigned int tmp_cpu;
 		u16 rxq_index;
-		u32 flow_id;
-		u32 hash;
 		int rc;
 
 		/* Should we steer this flow to a different hardware queue? */
@@ -4889,9 +4888,6 @@ set_rps_cpu(struct net_device *dev, struct sk_buff *skb,
 		if (!flow_table)
 			goto out;
 
-		hash = skb_get_hash(skb);
-		flow_id = rfs_slot(hash, flow_table);
-
 		tmp_rflow = &flow_table->flows[flow_id];
 		tmp_cpu = READ_ONCE(tmp_rflow->cpu);
 
@@ -4965,6 +4961,7 @@ static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
 	struct rps_dev_flow_table *flow_table;
 	struct rps_map *map;
 	int cpu = -1;
+	u32 flow_id;
 	u32 tcpu;
 	u32 hash;
 
@@ -5011,7 +5008,8 @@ static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
 		/* OK, now we know there is a match,
 		 * we can look at the local (per receive queue) flow table
 		 */
-		rflow = &flow_table->flows[rfs_slot(hash, flow_table)];
+		flow_id = rfs_slot(hash, flow_table);
+		rflow = &flow_table->flows[flow_id];
 		tcpu = rflow->cpu;
 
 		/*
@@ -5030,7 +5028,8 @@ static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
 		     ((int)(READ_ONCE(per_cpu(softnet_data, tcpu).input_queue_head) -
 		      rflow->last_qtail)) >= 0)) {
 			tcpu = next_cpu;
-			rflow = set_rps_cpu(dev, skb, rflow, next_cpu);
+			rflow = set_rps_cpu(dev, skb, rflow, next_cpu, hash,
+					    flow_id);
 		}
 
 		if (tcpu < nr_cpu_ids && cpu_online(tcpu)) {
-- 
2.43.0