From 87fb4b7b533073eeeaed0b6bf7c2328995f6c075 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 13 Oct 2011 07:28:54 +0000 Subject: [PATCH] net: more accurate skb truesize skb truesize currently accounts for sk_buff struct and part of skb head. kmalloc() roundings are also ignored. Considering that skb_shared_info is larger than sk_buff, its time to take it into account for better memory accounting. This patch introduces SKB_TRUESIZE(X) macro to centralize various assumptions into a single place. At skb alloc phase, we put skb_shared_info struct at the exact end of skb head, to allow a better use of memory (lowering number of reallocations), since kmalloc() gives us power-of-two memory blocks. Unless SLUB/SLUB debug is active, both skb->head and skb_shared_info are aligned to cache lines, as before. Note: This patch might trigger performance regressions because of misconfigured protocol stacks, hitting per socket or global memory limits that were previously not reached. But its a necessary step for a more accurate memory accounting. Signed-off-by: Eric Dumazet CC: Andi Kleen CC: Ben Hutchings Signed-off-by: David S. Miller --- include/linux/skbuff.h | 5 +++++ net/core/skbuff.c | 18 ++++++++++++++---- net/core/sock.c | 2 +- net/ipv4/icmp.c | 5 ++--- net/ipv4/tcp_input.c | 14 +++++++------- net/ipv6/icmp.c | 3 +-- net/iucv/af_iucv.c | 2 +- net/sctp/protocol.c | 2 +- 8 files changed, 32 insertions(+), 19 deletions(-) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index ac6b05a..64f8695 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -46,6 +46,11 @@ #define SKB_MAX_HEAD(X) (SKB_MAX_ORDER((X), 0)) #define SKB_MAX_ALLOC (SKB_MAX_ORDER(0, 2)) +/* return minimum truesize of one skb containing X bytes of data */ +#define SKB_TRUESIZE(X) ((X) + \ + SKB_DATA_ALIGN(sizeof(struct sk_buff)) + \ + SKB_DATA_ALIGN(sizeof(struct skb_shared_info))) + /* A. Checksumming of received packets by device. * * NONE: device failed to checksum this packet. diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 5b2c5f1..a7f855d 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -184,11 +184,20 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask, goto out; prefetchw(skb); - size = SKB_DATA_ALIGN(size); - data = kmalloc_node_track_caller(size + sizeof(struct skb_shared_info), - gfp_mask, node); + /* We do our best to align skb_shared_info on a separate cache + * line. It usually works because kmalloc(X > SMP_CACHE_BYTES) gives + * aligned memory blocks, unless SLUB/SLAB debug is enabled. + * Both skb->head and skb_shared_info are cache line aligned. + */ + size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info)); + data = kmalloc_node_track_caller(size, gfp_mask, node); if (!data) goto nodata; + /* kmalloc(size) might give us more room than requested. + * Put skb_shared_info exactly at the end of allocated zone, + * to allow max possible filling before reallocation. + */ + size = SKB_WITH_OVERHEAD(ksize(data)); prefetchw(data + size); /* @@ -197,7 +206,8 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask, * the tail pointer in struct sk_buff! */ memset(skb, 0, offsetof(struct sk_buff, tail)); - skb->truesize = size + sizeof(struct sk_buff); + /* Account for allocated memory : skb + skb->head */ + skb->truesize = SKB_TRUESIZE(size); atomic_set(&skb->users, 1); skb->head = data; skb->data = data; diff --git a/net/core/sock.c b/net/core/sock.c index 83c462d..5a08762 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -207,7 +207,7 @@ static struct lock_class_key af_callback_keys[AF_MAX]; * not depend upon such differences. */ #define _SK_MEM_PACKETS 256 -#define _SK_MEM_OVERHEAD (sizeof(struct sk_buff) + 256) +#define _SK_MEM_OVERHEAD SKB_TRUESIZE(256) #define SK_WMEM_MAX (_SK_MEM_OVERHEAD * _SK_MEM_PACKETS) #define SK_RMEM_MAX (_SK_MEM_OVERHEAD * _SK_MEM_PACKETS) diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c index 23ef31b..ab188ae 100644 --- a/net/ipv4/icmp.c +++ b/net/ipv4/icmp.c @@ -1152,10 +1152,9 @@ static int __net_init icmp_sk_init(struct net *net) net->ipv4.icmp_sk[i] = sk; /* Enough space for 2 64K ICMP packets, including - * sk_buff struct overhead. + * sk_buff/skb_shared_info struct overhead. */ - sk->sk_sndbuf = - (2 * ((64 * 1024) + sizeof(struct sk_buff))); + sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024); /* * Speedup sock_wfree() diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 81cae64..c1653fe 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -265,8 +265,7 @@ static inline int TCP_ECN_rcv_ecn_echo(struct tcp_sock *tp, struct tcphdr *th) static void tcp_fixup_sndbuf(struct sock *sk) { - int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 + - sizeof(struct sk_buff); + int sndmem = SKB_TRUESIZE(tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER); if (sk->sk_sndbuf < 3 * sndmem) { sk->sk_sndbuf = 3 * sndmem; @@ -349,7 +348,7 @@ static void tcp_grow_window(struct sock *sk, struct sk_buff *skb) static void tcp_fixup_rcvbuf(struct sock *sk) { struct tcp_sock *tp = tcp_sk(sk); - int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff); + int rcvmem = SKB_TRUESIZE(tp->advmss + MAX_TCP_HEADER); /* Try to select rcvbuf so that 4 mss-sized segments * will fit to window and corresponding skbs will fit to our rcvbuf. @@ -540,8 +539,7 @@ void tcp_rcv_space_adjust(struct sock *sk) space /= tp->advmss; if (!space) space = 1; - rcvmem = (tp->advmss + MAX_TCP_HEADER + - 16 + sizeof(struct sk_buff)); + rcvmem = SKB_TRUESIZE(tp->advmss + MAX_TCP_HEADER); while (tcp_win_from_space(rcvmem) < tp->advmss) rcvmem += 128; space *= rcvmem; @@ -4950,8 +4948,10 @@ static void tcp_new_space(struct sock *sk) struct tcp_sock *tp = tcp_sk(sk); if (tcp_should_expand_sndbuf(sk)) { - int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) + - MAX_TCP_HEADER + 16 + sizeof(struct sk_buff); + int sndmem = SKB_TRUESIZE(max_t(u32, + tp->rx_opt.mss_clamp, + tp->mss_cache) + + MAX_TCP_HEADER); int demanded = max_t(unsigned int, tp->snd_cwnd, tp->reordering + 1); sndmem *= 2 * demanded; diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c index 2b59154..90868fb 100644 --- a/net/ipv6/icmp.c +++ b/net/ipv6/icmp.c @@ -835,8 +835,7 @@ static int __net_init icmpv6_sk_init(struct net *net) /* Enough space for 2 64K ICMP packets, including * sk_buff struct overhead. */ - sk->sk_sndbuf = - (2 * ((64 * 1024) + sizeof(struct sk_buff))); + sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024); } return 0; diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c index c39f3a4..274d150 100644 --- a/net/iucv/af_iucv.c +++ b/net/iucv/af_iucv.c @@ -1819,7 +1819,7 @@ static void iucv_callback_rx(struct iucv_path *path, struct iucv_message *msg) goto save_message; len = atomic_read(&sk->sk_rmem_alloc); - len += iucv_msg_length(msg) + sizeof(struct sk_buff); + len += SKB_TRUESIZE(iucv_msg_length(msg)); if (len > sk->sk_rcvbuf) goto save_message; diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c index 91784f4..61b9fca 100644 --- a/net/sctp/protocol.c +++ b/net/sctp/protocol.c @@ -1299,7 +1299,7 @@ SCTP_STATIC __init int sctp_init(void) max_share = min(4UL*1024*1024, limit); sysctl_sctp_rmem[0] = SK_MEM_QUANTUM; /* give each asoc 1 page min */ - sysctl_sctp_rmem[1] = (1500 *(sizeof(struct sk_buff) + 1)); + sysctl_sctp_rmem[1] = 1500 * SKB_TRUESIZE(1); sysctl_sctp_rmem[2] = max(sysctl_sctp_rmem[1], max_share); sysctl_sctp_wmem[0] = SK_MEM_QUANTUM; -- 2.7.4