diff options
| author | Eric Dumazet <edumazet@google.com> | 2025-04-07 16:35:59 +0000 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2025-04-08 12:30:55 -0700 |
| commit | c3025e94daa9ce84ef0e53df983b5bf2fbd76ea6 (patch) | |
| tree | ae27369d8f8e2ba0f96e7038fa7a996d7d9c8d28 | |
| parent | 34a07c5b257453b5fcadc2408719c7b075844014 (diff) | |
net: rps: change skb_flow_limit() hash function
As explained in commit f3483c8e1da6 ("net: rfs: hash function change"),
masking low order bits of skb_get_hash(skb) has low entropy.
A NIC with 32 RX queues uses the 5 low order bits of rss key
to select a queue. This means all packets landing to a given
queue share the same 5 low order bits.
Switch to hash_32() to reduce hash collisions.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20250407163602.170356-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | net/core/dev.c | 2 | ||||
| -rw-r--r-- | net/core/dev.h | 2 | ||||
| -rw-r--r-- | net/core/sysctl_net_core.c | 2 |
3 files changed, 3 insertions, 3 deletions
diff --git a/net/core/dev.c b/net/core/dev.c index 0608605cfc24..f674236f34be 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -5038,7 +5038,7 @@ static bool skb_flow_limit(struct sk_buff *skb, unsigned int qlen) rcu_read_lock(); fl = rcu_dereference(sd->flow_limit); if (fl) { - new_flow = skb_get_hash(skb) & (fl->num_buckets - 1); + new_flow = hash_32(skb_get_hash(skb), fl->log_buckets); old_flow = fl->history[fl->history_head]; fl->history[fl->history_head] = new_flow; diff --git a/net/core/dev.h b/net/core/dev.h index 7ee203395d8e..b1cd44b5f009 100644 --- a/net/core/dev.h +++ b/net/core/dev.h @@ -16,7 +16,7 @@ struct cpumask; #define FLOW_LIMIT_HISTORY (1 << 7) /* must be ^2 and !overflow buckets */ struct sd_flow_limit { u64 count; - unsigned int num_buckets; + u8 log_buckets; unsigned int history_head; u16 history[FLOW_LIMIT_HISTORY]; u8 buckets[]; diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c index c7769ee0d9c5..5cfe76ede523 100644 --- a/net/core/sysctl_net_core.c +++ b/net/core/sysctl_net_core.c @@ -248,7 +248,7 @@ static int flow_limit_cpu_sysctl(const struct ctl_table *table, int write, ret = -ENOMEM; goto write_unlock; } - cur->num_buckets = netdev_flow_limit_table_len; + cur->log_buckets = ilog2(netdev_flow_limit_table_len); rcu_assign_pointer(sd->flow_limit, cur); } } |