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Date: Tue, 20 Jan 2009 02:14:19 -0800
From: Divy Le Ray <divy@...lsio.com>
To: herbert@...dor.apana.org.au
Cc: netdev@...r.kernel.org
Subject: Re: cxgb3: Replace LRO with GRO
Hi Herbert,
I have tried the following patch as an attempt to eliminate the memcpy
seen on the previous oprofile. I'm now getting about 5.5 Gbs.
After that, I went through the output of opreport -d to figure out
the most expensive ops witnessed in my profiling.
Here is the patch:
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2554,6 +2554,8 @@ struct sk_buff *napi_fraginfo_skb(struct napi_struct *napi,
struct net_device *dev = napi->dev;
struct sk_buff *skb = napi->skb;
struct ethhdr *eth;
+ skb_frag_t *frag;
+ int i;
napi->skb = NULL;
@@ -2566,9 +2568,15 @@ struct sk_buff *napi_fraginfo_skb(struct napi_struct *napi,
}
BUG_ON(info->nr_frags > MAX_SKB_FRAGS);
- skb_shinfo(skb)->nr_frags = info->nr_frags;
- memcpy(skb_shinfo(skb)->frags, info->frags, sizeof(info->frags));
+ frag = &info->frags[info->nr_frags - 1];
+ for (i = skb_shinfo(skb)->nr_frags; i < info->nr_frags; i++) {
+ skb_fill_page_desc(skb, i, frag->page, frag->page_offset,
+ frag->size);
+ frag++;
+ }
+ skb_shinfo(skb)->nr_frags = info->nr_frags;
+
skb->data_len = info->len;
skb->len += info->len;
skb->truesize += info->len;
Here is the non detailed opreport output for the CPU managing the reception
of netperf traffic:
38.815300 copy_user_generic_unrolled vmlinux
6.373900 process_responses cxgb3.ko
4.957800 inet_gro_receive vmlinux
4.908800 put_page vmlinux
4.862100 refill_fl cxgb3.ko
3.774900 dev_gro_receive vmlinux
3.096000 tcp_gro_receive vmlinux
2.764700 napi_fraginfo_skb vmlinux
2.174400 free_hot_cold_page vmlinux
2.006400 skb_copy_datagram_iovec vmlinux
1.511800 tcp_recvmsg vmlinux
1.488500 get_page_from_freelist vmlinux
1.455800 irq_entries_start vmlinux
1.453500 skb_gro_header vmlinux
0.877200 get_pageblock_flags_group vmlinux
0.863200 memcpy_toiovec vmlinux
0.856200 _raw_spin_lock vmlinux
0.720900 memcpy vmlinux
0.711600 skb_gro_receive vmlinux
0.683600 kfree vmlinux
Here is a list of more detailed info sorted per GRO function as seen above:
- Relative % for the most expensive instructions
- gdb dissass'output for these instructions
- gdb list's output.
inet_gro_receive 4.9578 ffffffff805468c0
ffffffff80546a49 11.1059%
0xffffffff80546a49 <inet_gro_receive+393>: jne 0xffffffff805469e5 <inet_gro_receive+293>
0xffffffff80546a49 is in inet_gro_receive (/mnt/net-2.6/net/ipv4/af_inet.c:1285).
1280 if (!NAPI_GRO_CB(p)->same_flow)
1281 continue;
1282
1283 iph2 = ip_hdr(p);
1284
1285 if (iph->protocol != iph2->protocol ||
1286 iph->tos != iph2->tos ||
1287 memcmp(&iph->saddr, &iph2->saddr, 8)) {
1288 NAPI_GRO_CB(p)->same_flow = 0;
1289 continue;
ffffffff80546a61 10.4000%
0xffffffff80546a61 <inet_gro_receive+417>: je 0xffffffff80546abb <inet_gro_receive+507>
0xffffffff80546a61 is in inet_gro_receive (/mnt/net-2.6/net/ipv4/af_inet.c:1293).
1288 NAPI_GRO_CB(p)->same_flow = 0;
1289 continue;
1290 }
1291
1292 /* All fields must match except length and checksum. */
1293 NAPI_GRO_CB(p)->flush |=
1294 memcmp(&iph->frag_off, &iph2->frag_off, 4) ||
1295 (u16)(ntohs(iph2->id) + NAPI_GRO_CB(p)->count) != id;
ffffffff80546a58 8.2353%
0xffffffff80546a58 <inet_gro_receive+408>: mov %rdx,%rcx
0xffffffff80546a58 is in inet_gro_receive (/mnt/net-2.6/net/ipv4/af_inet.c:1293).
1288 NAPI_GRO_CB(p)->same_flow = 0;
1289 continue;
1290 }
1291
1292 /* All fields must match except length and checksum. */
1293 NAPI_GRO_CB(p)->flush |=
1294 memcmp(&iph->frag_off, &iph2->frag_off, 4) ||
1295 (u16)(ntohs(iph2->id) + NAPI_GRO_CB(p)->count) != id;
1296
1297 NAPI_GRO_CB(p)->flush |= flush;
ffffffff80546abb 8.2353%
0xffffffff80546abb <inet_gro_receive+507>: movzwl 0x4(%r10),%eax
(gdb) list *(0xffffffff80546abb)
0xffffffff80546abb is in inet_gro_receive (/mnt/net-2.6/include/linux/swab.h:51).
46 static inline __attribute_const__ __u16 __fswab16(__u16 val)
47 {
48 #ifdef __arch_swab16
49 return __arch_swab16(val);
50 #else
51 return ___constant_swab16(val);
52 #endif
53 }
54
55 static inline __attribute_const__ __u32 __fswab32(__u32 val)
ffffffff80546a4b 8.1882%
0xffffffff80546a4b is in inet_gro_receive (/mnt/net-2.6/net/ipv4/af_inet.c:1293).
1288 NAPI_GRO_CB(p)->same_flow = 0;
1289 continue;
1290 }
1291
1292 /* All fields must match except length and checksum. */
1293 NAPI_GRO_CB(p)->flush |=
1294 memcmp(&iph->frag_off, &iph2->frag_off, 4) ||
1295 (u16)(ntohs(iph2->id) + NAPI_GRO_CB(p)->count) != id;
1296
1297 NAPI_GRO_CB(p)->flush |= flush;
ffffffff80546a47 7.5765%
0xffffffff80546a47 <inet_gro_receive+391>: repz cmpsb %es:(%rdi),%ds:(%rsi)
0xffffffff80546a47 is in inet_gro_receive (/mnt/net-2.6/net/ipv4/af_inet.c:1285).
1280 if (!NAPI_GRO_CB(p)->same_flow)
1281 continue;
1282
1283 iph2 = ip_hdr(p);
1284
1285 if (iph->protocol != iph2->protocol ||
1286 iph->tos != iph2->tos ||
1287 memcmp(&iph->saddr, &iph2->saddr, 8)) {
1288 NAPI_GRO_CB(p)->same_flow = 0;
1289 continue;
ffffffff80546a44 7.1529%
0xffffffff80546a44 is in inet_gro_receive (/mnt/net-2.6/net/ipv4/af_inet.c:1285).
1280 if (!NAPI_GRO_CB(p)->same_flow)
1281 continue;
1282
1283 iph2 = ip_hdr(p);
1284
1285 if (iph->protocol != iph2->protocol ||
1286 iph->tos != iph2->tos ||
1287 memcmp(&iph->saddr, &iph2->saddr, 8)) {
1288 NAPI_GRO_CB(p)->same_flow = 0;
1289 continue;
dev_gro_receive 3.7749 ffffffff805024b0
ffffffff805026a2 18.7268%
0xffffffff805026a2 <dev_gro_receive+498>: repz cmpsb %es:(%rdi),%ds:(%rsi)
0xffffffff805026a2 is in dev_gro_receive (/mnt/net-2.6/net/core/dev.c:2450).
2445 count++;
2446
2447 if (!NAPI_GRO_CB(p)->same_flow)
2448 continue;
2449
2450 if (p->mac_len != mac_len ||
2451 memcmp(skb_mac_header(p), mac, mac_len))
2452 NAPI_GRO_CB(p)->same_flow = 0;
2453 }
2454
ffffffff805026a4 13.4734%
0xffffffff805026a4 <dev_gro_receive+500>: je 0xffffffff805025c8 <dev_gro_receive+280>
(gdb) list *(0xffffffff805026a4)
0xffffffff805026a4 is in dev_gro_receive (/mnt/net-2.6/net/core/dev.c:2450).
2445 count++;
2446
2447 if (!NAPI_GRO_CB(p)->same_flow)
2448 continue;
2449
2450 if (p->mac_len != mac_len ||
2451 memcmp(skb_mac_header(p), mac, mac_len))
2452 NAPI_GRO_CB(p)->same_flow = 0;
ffffffff805025c8 9.3943%
0xffffffff805025c8 <dev_gro_receive+280>: mov (%r9),%r9
0xffffffff805025c8 is in dev_gro_receive (/mnt/net-2.6/net/core/dev.c:2444).
2439 skb->mac_len = mac_len;
2440 NAPI_GRO_CB(skb)->same_flow = 0;
2441 NAPI_GRO_CB(skb)->flush = 0;
2442 NAPI_GRO_CB(skb)->free = 0;
2443
2444 for (p = napi->gro_list; p; p = p->next) {
2445 count++;
2446
2447 if (!NAPI_GRO_CB(p)->same_flow)
2448 continue;
ffffffff805025f9 7.3548%
0xffffffff805025f9 <dev_gro_receive+329>: je 0xffffffff80502614 <dev_gro_receive+356>
0xffffffff805025f9 is in dev_gro_receive (/mnt/net-2.6/net/core/dev.c:2466).
2461 goto normal;
2462
2463 same_flow = NAPI_GRO_CB(skb)->same_flow;
2464 ret = NAPI_GRO_CB(skb)->free ? GRO_MERGED_FREE : GRO_MERGED;
2465
2466 if (pp) {
2467 struct sk_buff *nskb = *pp;
2468
2469 *pp = nskb->next;
2470 nskb->next = NULL;
tcp_gro_receive 3.0960 ffffffff80528df0
ffffffff80528f2b 16.3527%
0xffffffff80528f2b <tcp_gro_receive+315>: repz cmpsb %es:(%rdi),%ds:(%rsi)
0xffffffff80528f2b is in tcp_gro_receive (/mnt/net-2.6/net/ipv4/tcp.c:2521).
2516 flush = NAPI_GRO_CB(p)->flush;
2517 flush |= flags & TCP_FLAG_CWR;
2518 flush |= (flags ^ tcp_flag_word(th2)) &
2519 ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH);
2520 flush |= th->ack_seq != th2->ack_seq || th->window != th2->window;
2521 flush |= memcmp(th + 1, th2 + 1, thlen - sizeof(*th));
2522
2523 total = skb_gro_len(p);
2524 mss = skb_shinfo(p)->gso_size;
ffffffff80528f2d 15.9759%
0xffffffff80528f2d <tcp_gro_receive+317>: mov 0x60(%r8),%edi
0xffffffff80528f2d is in tcp_gro_receive (/mnt/net-2.6/include/linux/netdevice.h:1101).
1096 return NAPI_GRO_CB(skb)->data_offset;
1097 }
1098
1099 static inline unsigned int skb_gro_len(const struct sk_buff *skb)
1100 {
1101 return skb->len - NAPI_GRO_CB(skb)->data_offset;
1102 }
1103
1104 static inline void skb_gro_pull(struct sk_buff *skb, unsigned int len)
1105 {
ffffffff80528f31 13.7905%
0xffffffff80528f31 <tcp_gro_receive+321>: setb %al
0xffffffff80528f31 is in tcp_gro_receive (/mnt/net-2.6/net/ipv4/tcp.c:2521).
2516 flush = NAPI_GRO_CB(p)->flush;
2517 flush |= flags & TCP_FLAG_CWR;
2518 flush |= (flags ^ tcp_flag_word(th2)) &
2519 ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH);
2520 flush |= th->ack_seq != th2->ack_seq || th->window != th2->window;
2521 flush |= memcmp(th + 1, th2 + 1, thlen - sizeof(*th));
2522
2523 total = skb_gro_len(p);
2524 mss = skb_shinfo(p)->gso_size;
napi_fraginfo_skb 2.7647 ffffffff80501dd0
ffffffff80501f16 65.2321%
0xffffffff80501f16 <napi_fraginfo_skb+326>: mov %eax,0x6c(%rbx)
0xffffffff80501f16 is in napi_fraginfo_skb (/mnt/net-2.6/net/core/dev.c:2606).
2601 * special handling. We'll fix it up properly at the end.
2602 */
2603 skb->protocol = eth->h_proto;
2604
2605 skb->ip_summed = info->ip_summed;
2606 skb->csum = info->csum;
2607
2608 out:
2609 return skb;
2610 }
Cheers,
Divy
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