diff options
| author | Eric Dumazet <edumazet@google.com> | 2025-09-28 08:49:33 +0000 |
|---|---|---|
| committer | Paolo Abeni <pabeni@redhat.com> | 2025-09-30 15:45:53 +0200 |
| commit | 844c9db7f7f5fe1b0b53ed9f1c2bc7313b3021c8 (patch) | |
| tree | 9dd9c2e17b08ae6dd785ea2e7dbf7ac65c3f70f6 | |
| parent | 9c94ae6bb0b2895024b6e29fcc1cbec968b4776a (diff) | |
net: use llist for sd->defer_list
Get rid of sd->defer_lock and adopt llist operations.
We optimize skb_attempt_defer_free() for the common case,
where the packet is queued. Otherwise sd->defer_count
is increasing, until skb_defer_free_flush() clears it.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250928084934.3266948-3-edumazet@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
| -rw-r--r-- | include/linux/netdevice.h | 8 | ||||
| -rw-r--r-- | net/core/dev.c | 18 | ||||
| -rw-r--r-- | net/core/skbuff.c | 15 |
3 files changed, 17 insertions, 24 deletions
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 27e3fa69253f..5c9aa16933d1 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -3537,10 +3537,10 @@ struct softnet_data { struct numa_drop_counters drop_counters; /* Another possibly contended cache line */ - spinlock_t defer_lock ____cacheline_aligned_in_smp; - atomic_t defer_count; - int defer_ipi_scheduled; - struct sk_buff *defer_list; + struct llist_head defer_list ____cacheline_aligned_in_smp; + atomic_long_t defer_count; + + int defer_ipi_scheduled ____cacheline_aligned_in_smp; call_single_data_t defer_csd; }; diff --git a/net/core/dev.c b/net/core/dev.c index 8566678d8344..fb67372774de 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6717,22 +6717,16 @@ EXPORT_SYMBOL(napi_complete_done); static void skb_defer_free_flush(struct softnet_data *sd) { + struct llist_node *free_list; struct sk_buff *skb, *next; - /* Paired with WRITE_ONCE() in skb_attempt_defer_free() */ - if (!READ_ONCE(sd->defer_list)) + if (llist_empty(&sd->defer_list)) return; + atomic_long_set(&sd->defer_count, 0); + free_list = llist_del_all(&sd->defer_list); - spin_lock(&sd->defer_lock); - skb = sd->defer_list; - sd->defer_list = NULL; - atomic_set(&sd->defer_count, 0); - spin_unlock(&sd->defer_lock); - - while (skb != NULL) { - next = skb->next; + llist_for_each_entry_safe(skb, next, free_list, ll_node) { napi_consume_skb(skb, 1); - skb = next; } } @@ -12995,7 +12989,7 @@ static int __init net_dev_init(void) sd->cpu = i; #endif INIT_CSD(&sd->defer_csd, trigger_rx_softirq, sd); - spin_lock_init(&sd->defer_lock); + init_llist_head(&sd->defer_list); gro_init(&sd->backlog.gro); sd->backlog.poll = process_backlog; diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 16cd357d62a6..17455fc1e692 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -7185,6 +7185,7 @@ static void kfree_skb_napi_cache(struct sk_buff *skb) */ void skb_attempt_defer_free(struct sk_buff *skb) { + unsigned long defer_count; int cpu = skb->alloc_cpu; struct softnet_data *sd; unsigned int defer_max; @@ -7202,17 +7203,15 @@ nodefer: kfree_skb_napi_cache(skb); sd = &per_cpu(softnet_data, cpu); defer_max = READ_ONCE(net_hotdata.sysctl_skb_defer_max); - if (atomic_read(&sd->defer_count) >= defer_max) + defer_count = atomic_long_inc_return(&sd->defer_count); + + if (defer_count >= defer_max) goto nodefer; - spin_lock_bh(&sd->defer_lock); - /* Send an IPI every time queue reaches half capacity. */ - kick = (atomic_inc_return(&sd->defer_count) - 1) == (defer_max >> 1); + llist_add(&skb->ll_node, &sd->defer_list); - skb->next = sd->defer_list; - /* Paired with READ_ONCE() in skb_defer_free_flush() */ - WRITE_ONCE(sd->defer_list, skb); - spin_unlock_bh(&sd->defer_lock); + /* Send an IPI every time queue reaches half capacity. */ + kick = (defer_count - 1) == (defer_max >> 1); /* Make sure to trigger NET_RX_SOFTIRQ on the remote CPU * if we are unlucky enough (this seems very unlikely). |