Andrew & David- Attached is the skbinit patch for 2.5.38 kernel. The results of SPECWeb99 were posted to lkml using this patch. It showed 1.2% improvement in conforming connections. The results can be found at: http://marc.theaimsgroup.com/?l=lse-tech&m=103014598223558&w=2 I posted this patch as an RFC to lkml and the details can be found here: http://marc.theaimsgroup.com/?l=linux-kernel&m=102994936831586&w=2 The patch is very simple moving the initialization of skb from __kfree_skb to alloc_skb. Slab cache preserves the value of the objects between uses. Looks like we were trying to take advantage of this feature by initializing before freeing it and this is good for UNI but for SMP there is no guarantee that the freed skbs will be given back to the same CPU. The following are the results running Netperf3: Pentium III 998 MHz 2-way system Netperf3 tcp_stream test on an 2-way system using 2.5.38 SMP kernel. One adapter one connection test with 64k socket buffer and tcp no-delay ON. NAPI and TSO are disabled. 2.5.38 2.5.40+patch % Improvment Msg size Throughput Throughput (bytes) Mbits/sec Mbits/sec 512 568.7 579.8 2.0 1024 629.9 638.5 1.4 2048 673.4 682.1 1.3 4096 720.9 732.3 1.6 8192 779.6 799.8 2.6 16384 809.8 828.9 2.4 32768 757.6 772.1 1.9 65536 743.9 764.8 2.8 2.5.38 kernel baseline profile for 512 msg size - routines affected by the patch: c02b09f0 alloc_skb 557 c02b0c40 skb_release_data 879 c02b0cf0 kfree_skbmem 262 c02b0d60 __kfree_skb 1302 Total ticks spent in these routines: 3000 2.5.38 kernel+skbinit patch profile for 512 msg size - routines affected by the patch: c02b09f0 alloc_skb 987 c02b0ca0 skb_release_data 671 c02b0d50 kfree_skbmem 262 c02b0dc0 __kfree_skb 1008 Total ticks spent in these routines: 2928 Let me know if you need more data.I realize the performance gain is not substantial on the two workloads we tested. However the patch is simple, safe and improves network performance to some extent. diff -Naur linux-2538s/net/core/skbuff.c linux-2538skbinit/net/core/skbuff.c --- linux-2538s/net/core/skbuff.c Wed Sep 25 10:58:25 2002 +++ linux-2538skbinit/net/core/skbuff.c Tue Oct 8 11:38:35 2002 @@ -195,18 +195,38 @@ goto nodata; /* XXX: does not include slab overhead */ + skb->next = skb->prev = NULL; + skb->list = NULL; + skb->sk = NULL; + skb->stamp.tv_sec = 0; /* No idea about time */ + skb->dev = NULL; + skb->dst = NULL; + memset(skb->cb, 0, sizeof(skb->cb)); + skb->len = 0; + skb->data_len = 0; + skb->csum = 0; + skb->cloned = 0; + skb->pkt_type = PACKET_HOST; /* Default type */ + skb->ip_summed = 0; + skb->priority = 0; + atomic_set(&skb->users,1); + skb->security = 0; /* By default packets are insecure */ skb->truesize = size + sizeof(struct sk_buff); /* Load the data pointers. */ skb->head = skb->data = skb->tail = data; skb->end = data + size; - - /* Set up other state */ - skb->len = 0; - skb->cloned = 0; - skb->data_len = 0; - - atomic_set(&skb->users, 1); + skb->destructor = NULL; +#ifdef CONFIG_NETFILTER + skb->nfmark = skb->nfcache = 0; + skb->nfct = NULL; +#ifdef CONFIG_NETFILTER_DEBUG + skb->nf_debug = 0; +#endif +#endif +#ifdef CONFIG_NET_SCHED + skb->tc_index = 0; +#endif atomic_set(&(skb_shinfo(skb)->dataref), 1); skb_shinfo(skb)->nr_frags = 0; skb_shinfo(skb)->tso_size = 0; @@ -220,7 +240,6 @@ goto out; } - /* * Slab constructor for a skb head. */ @@ -328,7 +347,6 @@ #ifdef CONFIG_NETFILTER nf_conntrack_put(skb->nfct); #endif - skb_headerinit(skb, NULL, 0); /* clean state */ kfree_skbmem(skb); } @@ -1204,7 +1222,7 @@ sizeof(struct sk_buff), 0, SLAB_HWCACHE_ALIGN, - skb_headerinit, NULL); + NULL, NULL); if (!skbuff_head_cache) panic("cannot create skbuff cache"); Regards, Mala Mala Anand IBM Linux Technology Center E-mail:mkanand@us.ibm.com http://www-124.ibm.com/developerworks/opensource/linuxperf Phone:512-838-8088 - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
