[net-next PATCH 6/7] net: introduce napi_alloc_skb_hint() for more use-cases

[Jesper Dangaard Brouer]

The default bulk alloc size arbitrarily choosen (to be 8) might
not suit all use-cases, this introduce a function napi_alloc_skb_hint()
that allow the caller to specify a bulk size hint they are expecting.
It is a hint because __napi_alloc_skb() limits the bulk size to
the array size.

One user is the mlx5 driver, which bulk re-populate it's RX ring
with both SKBs and pages.  Thus, it would like to work with
bigger bulk alloc chunks.

Signed-off-by: Jesper Dangaard Brouer <bro...@redhat.com>
---
 include/linux/skbuff.h |   19 +++++++++++++++----
 net/core/skbuff.c      |    8 +++-----
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 797cefb888fb..f49077caedaf 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2393,14 +2393,25 @@ static inline void skb_free_frag(void *addr)
        __free_page_frag(addr);
 }
 
+#define NAPI_SKB_CACHE_SIZE    64U /* Used in struct napi_alloc_cache */
+#define NAPI_SKB_BULK_ALLOC     8U /* Default slab bulk alloc in NAPI */
+
 void *napi_alloc_frag(unsigned int fragsz);
-struct sk_buff *__napi_alloc_skb(struct napi_struct *napi,
-                                unsigned int length, gfp_t gfp_mask);
+struct sk_buff *__napi_alloc_skb(struct napi_struct *napi, unsigned int len,
+                                unsigned int bulk_hint, gfp_t gfp_mask);
 static inline struct sk_buff *napi_alloc_skb(struct napi_struct *napi,
-                                            unsigned int length)
+                                            unsigned int len)
+{
+       return __napi_alloc_skb(napi, len, NAPI_SKB_BULK_ALLOC, GFP_ATOMIC);
+}
+static inline struct sk_buff *napi_alloc_skb_hint(struct napi_struct *napi,
+                                                 unsigned int len,
+                                                 unsigned int bulk_hint)
 {
-       return __napi_alloc_skb(napi, length, GFP_ATOMIC);
+       bulk_hint = bulk_hint ? : 1;
+       return __napi_alloc_skb(napi, len, bulk_hint, GFP_ATOMIC);
 }
+
 void napi_consume_skb(struct sk_buff *skb, int budget);
 
 void __kfree_skb_flush(void);
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 96fb7933b614..c770bd4391ab 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -359,8 +359,6 @@ struct sk_buff *build_skb(void *data, unsigned int 
frag_size)
 }
 EXPORT_SYMBOL(build_skb);
 
-#define NAPI_SKB_CACHE_SIZE    64
-
 struct napi_alloc_cache {
        struct page_frag_cache page;
        size_t skb_count;
@@ -492,9 +490,10 @@ EXPORT_SYMBOL(__netdev_alloc_skb);
  *     %NULL is returned if there is no free memory.
  */
 struct sk_buff *__napi_alloc_skb(struct napi_struct *napi, unsigned int len,
-                                gfp_t gfp_mask)
+                                unsigned int bulk_hint, gfp_t gfp_mask)
 {
        struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache);
+       unsigned int bulk_sz = min(bulk_hint, NAPI_SKB_CACHE_SIZE);
        struct sk_buff *skb;
        void *data;
 
@@ -518,10 +517,9 @@ struct sk_buff *__napi_alloc_skb(struct napi_struct *napi, 
unsigned int len,
        if (unlikely(!data))
                return NULL;
 
-#define BULK_ALLOC_SIZE 8
        if (!nc->skb_count) {
                nc->skb_count = kmem_cache_alloc_bulk(skbuff_head_cache,
-                                                     gfp_mask, BULK_ALLOC_SIZE,
+                                                     gfp_mask, bulk_sz,
                                                      nc->skb_cache);
        }
        if (likely(nc->skb_count)) {