[PATCH v5 net-next 11/11] skbuff: queue NAPI_MERGED_FREE skbs into NAPI cache instead of freeing

From: Alexander Lobakin
Date: Thu Feb 11 2021 - 14:01:11 EST


napi_frags_finish() and napi_skb_finish() can only be called inside
NAPI Rx context, so we can feed NAPI cache with skbuff_heads that
got NAPI_MERGED_FREE verdict instead of immediate freeing.
Replace __kfree_skb() with __kfree_skb_defer() in napi_skb_finish()
and move napi_skb_free_stolen_head() to skbuff.c, so it can drop skbs
to NAPI cache.
As many drivers call napi_alloc_skb()/napi_get_frags() on their
receive path, this becomes especially useful.

Signed-off-by: Alexander Lobakin <alobakin@xxxxx>
---
include/linux/skbuff.h | 1 +
net/core/dev.c | 9 +--------
net/core/skbuff.c | 12 +++++++++---
3 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 906122eac82a..6d0a33d1c0db 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2921,6 +2921,7 @@ static inline struct sk_buff *napi_alloc_skb(struct napi_struct *napi,
}
void napi_consume_skb(struct sk_buff *skb, int budget);

+void napi_skb_free_stolen_head(struct sk_buff *skb);
void __kfree_skb_defer(struct sk_buff *skb);

/**
diff --git a/net/core/dev.c b/net/core/dev.c
index 4154d4683bb9..6d2c7ae90a23 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6095,13 +6095,6 @@ struct packet_offload *gro_find_complete_by_type(__be16 type)
}
EXPORT_SYMBOL(gro_find_complete_by_type);

-static void napi_skb_free_stolen_head(struct sk_buff *skb)
-{
- skb_dst_drop(skb);
- skb_ext_put(skb);
- kmem_cache_free(skbuff_head_cache, skb);
-}
-
static gro_result_t napi_skb_finish(struct napi_struct *napi,
struct sk_buff *skb,
gro_result_t ret)
@@ -6115,7 +6108,7 @@ static gro_result_t napi_skb_finish(struct napi_struct *napi,
if (NAPI_GRO_CB(skb)->free == NAPI_GRO_FREE_STOLEN_HEAD)
napi_skb_free_stolen_head(skb);
else
- __kfree_skb(skb);
+ __kfree_skb_defer(skb);
break;

case GRO_HELD:
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index c8f3ea1d9fbb..85f0768a1144 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -917,9 +917,6 @@ static void napi_skb_cache_put(struct sk_buff *skb)
struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache);
u32 i;

- /* drop skb->head and call any destructors for packet */
- skb_release_all(skb);
-
kasan_poison_object_data(skbuff_head_cache, skb);
nc->skb_cache[nc->skb_count++] = skb;

@@ -936,6 +933,14 @@ static void napi_skb_cache_put(struct sk_buff *skb)

void __kfree_skb_defer(struct sk_buff *skb)
{
+ skb_release_all(skb);
+ napi_skb_cache_put(skb);
+}
+
+void napi_skb_free_stolen_head(struct sk_buff *skb)
+{
+ skb_dst_drop(skb);
+ skb_ext_put(skb);
napi_skb_cache_put(skb);
}

@@ -961,6 +966,7 @@ void napi_consume_skb(struct sk_buff *skb, int budget)
return;
}

+ skb_release_all(skb);
napi_skb_cache_put(skb);
}
EXPORT_SYMBOL(napi_consume_skb);
--
2.30.1