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net: make GRO aware of skb->head_frag 

GRO can check if skb to be merged has its skb->head mapped to a page
fragment, instead of a kmalloc() area.

We 'upgrade' skb->head as a fragment in itself

This avoids the frag_list fallback, and permits to build true GRO skb
(one sk_buff and up to 16 fragments), using less memory.

This reduces number of cache misses when user makes its copy, since a
single sk_buff is fetched.

This is a followup of patch "net: allow skb->head to be a page fragment"

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Maciej Żenczykowski <maze@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Tom Herbert <therbert@google.com>
Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
Cc: Matt Carlson <mcarlson@broadcom.com>
Cc: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2012-04-30 08:10:34 +00:00 committed by David S. Miller
parent 8d4057a938
commit d7e8883cfc
4 changed files with 33 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/netdevice.h
View File

@ -1509,6 +1509,8 @@ struct napi_gro_cb {
/* Free the skb? */
int free;
#define NAPI_GRO_FREE 1
#define NAPI_GRO_FREE_STOLEN_HEAD 2
};
#define NAPI_GRO_CB(skb) ((struct napi_gro_cb *)(skb)->cb)

1
include/linux/skbuff.h
View File

@ -561,6 +561,7 @@ static inline struct rtable *skb_rtable(const struct sk_buff *skb)
extern void kfree_skb(struct sk_buff *skb);
extern void consume_skb(struct sk_buff *skb);
extern void __kfree_skb(struct sk_buff *skb);
extern struct kmem_cache *skbuff_head_cache;
extern struct sk_buff *__alloc_skb(unsigned int size,
gfp_t priority, int fclone, int node);
extern struct sk_buff *build_skb(void *data, unsigned int frag_size);

5
net/core/dev.c
View File

@ -3546,7 +3546,10 @@ gro_result_t napi_skb_finish(gro_result_t ret, struct sk_buff *skb)
break;
case GRO_MERGED_FREE:
consume_skb(skb);
if (NAPI_GRO_CB(skb)->free == NAPI_GRO_FREE_STOLEN_HEAD)
kmem_cache_free(skbuff_head_cache, skb);
else
__kfree_skb(skb);
break;
case GRO_HELD:

27
net/core/skbuff.c
View File

@ -69,7 +69,7 @@
#include <trace/events/skb.h>
#include <linux/highmem.h>
static struct kmem_cache *skbuff_head_cache __read_mostly;
struct kmem_cache *skbuff_head_cache __read_mostly;
static struct kmem_cache *skbuff_fclone_cache __read_mostly;
static void sock_pipe_buf_release(struct pipe_inode_info *pipe,
@ -2901,6 +2901,31 @@ int skb_gro_receive(struct sk_buff **head, struct sk_buff *skb)
NAPI_GRO_CB(skb)->free = 1;
goto done;
} else if (skb->head_frag) {
int nr_frags = pinfo->nr_frags;
skb_frag_t *frag = pinfo->frags + nr_frags;
struct page *page = virt_to_head_page(skb->head);
unsigned int first_size = headlen - offset;
unsigned int first_offset;
if (nr_frags + 1 + skbinfo->nr_frags > MAX_SKB_FRAGS)
return -E2BIG;
first_offset = skb->data -
(unsigned char *)page_address(page) +
offset;
pinfo->nr_frags = nr_frags + 1 + skbinfo->nr_frags;
frag->page.p = page;
frag->page_offset = first_offset;
skb_frag_size_set(frag, first_size);
memcpy(frag + 1, skbinfo->frags, sizeof(*frag) * skbinfo->nr_frags);
/* We dont need to clear skbinfo->nr_frags here */
NAPI_GRO_CB(skb)->free = NAPI_GRO_FREE_STOLEN_HEAD;
goto done;
} else if (skb_gro_len(p) != pinfo->gso_size)
return -E2BIG;