mirrors/linux
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2025-12-28 07:54:36 -05:00
Code Issues Packages Projects Releases Wiki Activity

net: rps: change skb_flow_limit() hash function

Browse Source 
As explained in commit f3483c8e1d ("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>
This commit is contained in:
Eric Dumazet
2025-04-07 16:35:59 +00:00
committed by Jakub Kicinski
parent 34a07c5b25
commit c3025e94da
3 changed files with 3 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
net/core/dev.c
View File

@@ -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;

2
net/core/dev.h
View File

@@ -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[];

2
net/core/sysctl_net_core.c
View File

@@ -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);
}
}