Re: [PATCH net-next] net: add skb allocation flags to __pskb_copy

[Christoph Paasch <christoph.paasch@uclouvain.be>]

Hello Octavian,

On 07/06/14 - 22:19:29, Octavian Purdila wrote:
> There are several instances where a __pskb_copy is immediately
> followed by an skb_clone. Add a new parameter to __pskb_copy to allow
> the skb to be allocated from the fclone cache and thus speed up
> subsequent skb_clone calls.
> 
> Signed-off-by: Octavian Purdila <octavian.purdila@intel.com>
> ---
>  include/linux/skbuff.h   | 6 +++---
>  net/bluetooth/hci_sock.c | 5 +++--
>  net/core/skbuff.c        | 7 +++++--
>  net/ipv4/tcp_output.c    | 2 +-
>  net/nfc/llcp_core.c      | 2 +-
>  net/nfc/rawsock.c        | 2 +-
>  6 files changed, 14 insertions(+), 10 deletions(-)

I found two more cases where the stack could benefit from using an FCLONE:

* batadv_nc_skb_store_before_coding() does a pskb_copy and later in
  batadv_nc_skb_store_for_decoding() the skb_clone is done.

* tipc_bcbearer_send() also does a pskb_copy, and the send_msg-callback (in
  tipc_bearer_send()) does a clone too later on in tipc_l2_send_msg().


Cheers,
Christoph

> 
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index c705808..7c5b56a 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -744,8 +744,8 @@ struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src);
>  int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask);
>  struct sk_buff *skb_clone(struct sk_buff *skb, gfp_t priority);
>  struct sk_buff *skb_copy(const struct sk_buff *skb, gfp_t priority);
> -struct sk_buff *__pskb_copy(struct sk_buff *skb, int headroom, gfp_t gfp_mask);
> -
> +struct sk_buff *__pskb_copy(struct sk_buff *skb, int headroom, gfp_t gfp_mask,
> +			    int flags);
>  int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, gfp_t gfp_mask);
>  struct sk_buff *skb_realloc_headroom(struct sk_buff *skb,
>  				     unsigned int headroom);
> @@ -2235,7 +2235,7 @@ static inline dma_addr_t skb_frag_dma_map(struct device *dev,
>  static inline struct sk_buff *pskb_copy(struct sk_buff *skb,
>  					gfp_t gfp_mask)
>  {
> -	return __pskb_copy(skb, skb_headroom(skb), gfp_mask);
> +	return __pskb_copy(skb, skb_headroom(skb), gfp_mask, 0);
>  }
>  
>  /**
> diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
> index f608bff..c2f5db3 100644
> --- a/net/bluetooth/hci_sock.c
> +++ b/net/bluetooth/hci_sock.c
> @@ -143,7 +143,8 @@ void hci_send_to_sock(struct hci_dev *hdev, struct sk_buff *skb)
>  
>  		if (!skb_copy) {
>  			/* Create a private copy with headroom */
> -			skb_copy = __pskb_copy(skb, 1, GFP_ATOMIC);
> +			skb_copy = __pskb_copy(skb, 1, GFP_ATOMIC,
> +					       SKB_ALLOC_FCLONE);
>  			if (!skb_copy)
>  				continue;
>  
> @@ -248,7 +249,7 @@ void hci_send_to_monitor(struct hci_dev *hdev, struct sk_buff *skb)
>  
>  			/* Create a private copy with headroom */
>  			skb_copy = __pskb_copy(skb, HCI_MON_HDR_SIZE,
> -					       GFP_ATOMIC);
> +					       GFP_ATOMIC, SKB_ALLOC_FCLONE);
>  			if (!skb_copy)
>  				continue;
>  
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 05f4bef..03863be 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -955,6 +955,7 @@ EXPORT_SYMBOL(skb_copy);
>   *	@skb: buffer to copy
>   *	@headroom: headroom of new skb
>   *	@gfp_mask: allocation priority
> + *	@flags: skb allocation flags (e.g. SKB_ALLOC_FCLONE)
>   *
>   *	Make a copy of both an &sk_buff and part of its data, located
>   *	in header. Fragmented data remain shared. This is used when
> @@ -964,11 +965,13 @@ EXPORT_SYMBOL(skb_copy);
>   *	The returned buffer has a reference count of 1.
>   */
>  
> -struct sk_buff *__pskb_copy(struct sk_buff *skb, int headroom, gfp_t gfp_mask)
> +struct sk_buff *__pskb_copy(struct sk_buff *skb, int headroom, gfp_t gfp_mask,
> +			    int flags)
>  {
>  	unsigned int size = skb_headlen(skb) + headroom;
>  	struct sk_buff *n = __alloc_skb(size, gfp_mask,
> -					skb_alloc_rx_flag(skb), NUMA_NO_NODE);
> +					flags | skb_alloc_rx_flag(skb),
> +					NUMA_NO_NODE);
>  
>  	if (!n)
>  		goto out;
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index d463c35..17fe18d 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -2490,7 +2490,7 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
>  	if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) ||
>  		     skb_headroom(skb) >= 0xFFFF)) {
>  		struct sk_buff *nskb = __pskb_copy(skb, MAX_TCP_HEADER,
> -						   GFP_ATOMIC);
> +						   GFP_ATOMIC, 0);
>  		err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
>  			     -ENOBUFS;
>  	} else {
> diff --git a/net/nfc/llcp_core.c b/net/nfc/llcp_core.c
> index f6278da..df960a3 100644
> --- a/net/nfc/llcp_core.c
> +++ b/net/nfc/llcp_core.c
> @@ -681,7 +681,7 @@ void nfc_llcp_send_to_raw_sock(struct nfc_llcp_local *local,
>  
>  		if (skb_copy == NULL) {
>  			skb_copy = __pskb_copy(skb, NFC_RAW_HEADER_SIZE,
> -					       GFP_ATOMIC);
> +					       GFP_ATOMIC, SKB_ALLOC_FCLONE);
>  
>  			if (skb_copy == NULL)
>  				continue;
> diff --git a/net/nfc/rawsock.c b/net/nfc/rawsock.c
> index 55eefee..e8c1805 100644
> --- a/net/nfc/rawsock.c
> +++ b/net/nfc/rawsock.c
> @@ -379,7 +379,7 @@ void nfc_send_to_raw_sock(struct nfc_dev *dev, struct sk_buff *skb,
>  	sk_for_each(sk, &raw_sk_list.head) {
>  		if (!skb_copy) {
>  			skb_copy = __pskb_copy(skb, NFC_RAW_HEADER_SIZE,
> -				     GFP_ATOMIC);
> +					       GFP_ATOMIC, SKB_ALLOC_FCLONE);
>  			if (!skb_copy)
>  				continue;
>  
> -- 
> 1.8.3.2
>