From d179cd12928443f3ec29cfbc3567439644bd0afc Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Wed, 17 Aug 2005 14:57:30 -0700 Subject: [PATCH] [NET]: Implement SKB fast cloning. Protocols that make extensive use of SKB cloning, for example TCP, eat at least 2 allocations per packet sent as a result. To cut the kmalloc() count in half, we implement a pre-allocation scheme wherein we allocate 2 sk_buff objects in advance, then use a simple reference count to free up the memory at the correct time. Based upon an initial patch by Thomas Graf and suggestions from Herbert Xu. Signed-off-by: David S. Miller --- include/linux/skbuff.h | 26 ++++++++++++-- include/net/sock.h | 2 +- net/core/skbuff.c | 82 ++++++++++++++++++++++++++++++++++++------ net/ipv4/tcp_output.c | 4 +-- 4 files changed, 98 insertions(+), 16 deletions(-) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index db10335e4192..42edce6abe23 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -162,6 +162,13 @@ struct skb_timeval { u32 off_usec; }; + +enum { + SKB_FCLONE_UNAVAILABLE, + SKB_FCLONE_ORIG, + SKB_FCLONE_CLONE, +}; + /** * struct sk_buff - socket buffer * @next: Next buffer in list @@ -255,7 +262,8 @@ struct sk_buff { ip_summed:2, nohdr:1, nfctinfo:3; - __u8 pkt_type; + __u8 pkt_type:3, + fclone:2; __be16 protocol; void (*destructor)(struct sk_buff *skb); @@ -295,8 +303,20 @@ struct sk_buff { #include extern void __kfree_skb(struct sk_buff *skb); -extern struct sk_buff *alloc_skb(unsigned int size, - unsigned int __nocast priority); +extern struct sk_buff *__alloc_skb(unsigned int size, + unsigned int __nocast priority, int fclone); +static inline struct sk_buff *alloc_skb(unsigned int size, + unsigned int __nocast priority) +{ + return __alloc_skb(size, priority, 0); +} + +static inline struct sk_buff *alloc_skb_fclone(unsigned int size, + unsigned int __nocast priority) +{ + return __alloc_skb(size, priority, 1); +} + extern struct sk_buff *alloc_skb_from_cache(kmem_cache_t *cp, unsigned int size, unsigned int __nocast priority); diff --git a/include/net/sock.h b/include/net/sock.h index 14183883e8e6..d57aece9492c 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -1200,7 +1200,7 @@ static inline struct sk_buff *sk_stream_alloc_pskb(struct sock *sk, int hdr_len; hdr_len = SKB_DATA_ALIGN(sk->sk_prot->max_header); - skb = alloc_skb(size + hdr_len, gfp); + skb = alloc_skb_fclone(size + hdr_len, gfp); if (skb) { skb->truesize += mem; if (sk->sk_forward_alloc >= (int)skb->truesize || diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 39a161dbc16d..b853a9b29eb6 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -69,6 +69,7 @@ #include static kmem_cache_t *skbuff_head_cache; +static kmem_cache_t *skbuff_fclone_cache; struct timeval __read_mostly skb_tv_base; @@ -120,7 +121,7 @@ void skb_under_panic(struct sk_buff *skb, int sz, void *here) */ /** - * alloc_skb - allocate a network buffer + * __alloc_skb - allocate a network buffer * @size: size to allocate * @gfp_mask: allocation mask * @@ -131,14 +132,20 @@ void skb_under_panic(struct sk_buff *skb, int sz, void *here) * Buffers may only be allocated from interrupts using a @gfp_mask of * %GFP_ATOMIC. */ -struct sk_buff *alloc_skb(unsigned int size, unsigned int __nocast gfp_mask) +struct sk_buff *__alloc_skb(unsigned int size, unsigned int __nocast gfp_mask, + int fclone) { struct sk_buff *skb; u8 *data; /* Get the HEAD */ - skb = kmem_cache_alloc(skbuff_head_cache, - gfp_mask & ~__GFP_DMA); + if (fclone) + skb = kmem_cache_alloc(skbuff_fclone_cache, + gfp_mask & ~__GFP_DMA); + else + skb = kmem_cache_alloc(skbuff_head_cache, + gfp_mask & ~__GFP_DMA); + if (!skb) goto out; @@ -155,7 +162,15 @@ struct sk_buff *alloc_skb(unsigned int size, unsigned int __nocast gfp_mask) skb->data = data; skb->tail = data; skb->end = data + size; + if (fclone) { + struct sk_buff *child = skb + 1; + atomic_t *fclone_ref = (atomic_t *) (child + 1); + skb->fclone = SKB_FCLONE_ORIG; + atomic_set(fclone_ref, 1); + + child->fclone = SKB_FCLONE_UNAVAILABLE; + } atomic_set(&(skb_shinfo(skb)->dataref), 1); skb_shinfo(skb)->nr_frags = 0; skb_shinfo(skb)->tso_size = 0; @@ -268,8 +283,34 @@ void skb_release_data(struct sk_buff *skb) */ void kfree_skbmem(struct sk_buff *skb) { + struct sk_buff *other; + atomic_t *fclone_ref; + skb_release_data(skb); - kmem_cache_free(skbuff_head_cache, skb); + switch (skb->fclone) { + case SKB_FCLONE_UNAVAILABLE: + kmem_cache_free(skbuff_head_cache, skb); + break; + + case SKB_FCLONE_ORIG: + fclone_ref = (atomic_t *) (skb + 2); + if (atomic_dec_and_test(fclone_ref)) + kmem_cache_free(skbuff_fclone_cache, skb); + break; + + case SKB_FCLONE_CLONE: + fclone_ref = (atomic_t *) (skb + 1); + other = skb - 1; + + /* The clone portion is available for + * fast-cloning again. + */ + skb->fclone = SKB_FCLONE_UNAVAILABLE; + + if (atomic_dec_and_test(fclone_ref)) + kmem_cache_free(skbuff_fclone_cache, other); + break; + }; } /** @@ -324,10 +365,20 @@ void __kfree_skb(struct sk_buff *skb) struct sk_buff *skb_clone(struct sk_buff *skb, unsigned int __nocast gfp_mask) { - struct sk_buff *n = kmem_cache_alloc(skbuff_head_cache, gfp_mask); - - if (!n) - return NULL; + struct sk_buff *n; + + n = skb + 1; + if (skb->fclone == SKB_FCLONE_ORIG && + n->fclone == SKB_FCLONE_UNAVAILABLE) { + atomic_t *fclone_ref = (atomic_t *) (n + 1); + n->fclone = SKB_FCLONE_CLONE; + atomic_inc(fclone_ref); + } else { + n = kmem_cache_alloc(skbuff_head_cache, gfp_mask); + if (!n) + return NULL; + n->fclone = SKB_FCLONE_UNAVAILABLE; + } #define C(x) n->x = skb->x @@ -409,6 +460,7 @@ static void copy_skb_header(struct sk_buff *new, const struct sk_buff *old) new->mac.raw = old->mac.raw + offset; memcpy(new->cb, old->cb, sizeof(old->cb)); new->local_df = old->local_df; + new->fclone = SKB_FCLONE_UNAVAILABLE; new->pkt_type = old->pkt_type; new->tstamp = old->tstamp; new->destructor = NULL; @@ -1647,13 +1699,23 @@ void __init skb_init(void) NULL, NULL); if (!skbuff_head_cache) panic("cannot create skbuff cache"); + + skbuff_fclone_cache = kmem_cache_create("skbuff_fclone_cache", + (2*sizeof(struct sk_buff)) + + sizeof(atomic_t), + 0, + SLAB_HWCACHE_ALIGN, + NULL, NULL); + if (!skbuff_fclone_cache) + panic("cannot create skbuff cache"); + do_gettimeofday(&skb_tv_base); } EXPORT_SYMBOL(___pskb_trim); EXPORT_SYMBOL(__kfree_skb); EXPORT_SYMBOL(__pskb_pull_tail); -EXPORT_SYMBOL(alloc_skb); +EXPORT_SYMBOL(__alloc_skb); EXPORT_SYMBOL(pskb_copy); EXPORT_SYMBOL(pskb_expand_head); EXPORT_SYMBOL(skb_checksum); diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 8d92ab562aed..75b68116682a 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1582,7 +1582,7 @@ void tcp_send_fin(struct sock *sk) } else { /* Socket is locked, keep trying until memory is available. */ for (;;) { - skb = alloc_skb(MAX_TCP_HEADER, GFP_KERNEL); + skb = alloc_skb_fclone(MAX_TCP_HEADER, GFP_KERNEL); if (skb) break; yield(); @@ -1804,7 +1804,7 @@ int tcp_connect(struct sock *sk) tcp_connect_init(sk); - buff = alloc_skb(MAX_TCP_HEADER + 15, sk->sk_allocation); + buff = alloc_skb_fclone(MAX_TCP_HEADER + 15, sk->sk_allocation); if (unlikely(buff == NULL)) return -ENOBUFS; -- GitLab