[PATCH net-next 4/5] skbuff: allocate skbuff_heads by bulks instead of one by one

[Alexander Lobakin <alobakin@pm.me>]

Use the same napi_alloc_cache struct and the same approach as used
for bulk-freeing skbuff_heads to allocate them for new skbs.
The new skb_cache will store up to NAPI_SKB_CACHE_SIZE (currently
64, which equals to NAPI_POLL_WEIGHT to be capable to serve one
polling cycle) and will be refilled by bulks in case of full
depletion or after completing network softirqs.

Signed-off-by: Alexander Lobakin <alobakin@pm.me>
---
 net/core/skbuff.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 0e8c597ff6ce..57a7307689f3 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -367,6 +367,8 @@ EXPORT_SYMBOL(build_skb_around);
 
 struct napi_alloc_cache {
 	struct page_frag_cache	page;
+	u32			skb_count;
+	void			*skb_cache[NAPI_SKB_CACHE_SIZE];
 	u32			flush_skb_count;
 	void			*flush_skb_cache[NAPI_SKB_CACHE_SIZE];
 };
@@ -490,7 +492,15 @@ static struct sk_buff *__napi_decache_skb(struct napi_alloc_cache *nc)
 	if (nc->flush_skb_count)
 		return nc->flush_skb_cache[--nc->flush_skb_count];
 
-	return kmem_cache_alloc(skbuff_head_cache, GFP_ATOMIC);
+	if (unlikely(!nc->skb_count))
+		nc->skb_count = kmem_cache_alloc_bulk(skbuff_head_cache,
+						      GFP_ATOMIC,
+						      NAPI_SKB_CACHE_SIZE,
+						      nc->skb_cache);
+	if (unlikely(!nc->skb_count))
+		return NULL;
+
+	return nc->skb_cache[--nc->skb_count];
 }
 
 /**
@@ -870,6 +880,7 @@ void __consume_stateless_skb(struct sk_buff *skb)
 void __kfree_skb_flush(void)
 {
 	struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache);
+	u32 num;
 
 	/* flush flush_skb_cache if containing objects */
 	if (nc->flush_skb_count) {
@@ -877,6 +888,13 @@ void __kfree_skb_flush(void)
 				     nc->flush_skb_cache);
 		nc->flush_skb_count = 0;
 	}
+
+	num = NAPI_SKB_CACHE_SIZE - nc->skb_count;
+	if (num)
+		nc->skb_count += kmem_cache_alloc_bulk(skbuff_head_cache,
+						       GFP_ATOMIC, num,
+						       nc->skb_cache +
+						       nc->skb_count);
 }
 
 static inline void _kfree_skb_defer(struct sk_buff *skb)
-- 
2.30.0