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Date: Tue, 25 Aug 2009 18:25:31 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: Stephen Hemminger <shemminger@...tta.com>
CC: David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
Robert Olsson <robert.olsson@....uu.se>
Subject: Re: Kernel forwarding performance test regressions
Stephen Hemminger a écrit :
> On Tue, 25 Aug 2009 11:47:58 +0200
> Eric Dumazet <eric.dumazet@...il.com> wrote:
>> Thats strange, because at Giga flood level, we should be on NAPI mode,
>> ksoftirqd using 100% of one cpu. SMP affinities should not matter at all...
>
> The transmit completions are still kicking off some interrupts.
Ah, yes, in my case, as I use same device for transmit, I had no addtional interrupts
>
>>> * unidirectional numbers are 2X the bidirectional numbers:
>>> 2.6.26 goes from 20% to 40%
>>>
>>> * this is single stream (doesn't help/use multiqueue)
>>>
>>> * system loads iptables but does not use it, so each packet
>>> sees the overhead of null rules.
>>>
>>> So kernel 2.6.29 had an observable dip in performance
>>> which seems to be mostly recovered in 2.6.30.
>>>
>>> These are from our QA, not me so please don't ask me for
>>> "please rerun with XX enabled", go run the same test
>>> yourself with pktgen.
>>>
>> Unfortunatly I cannot reach line-rate with pktgen and small packets.
>> (Limit ~1012333pps 485Mb/sec on my test machine, 3GHz E5450 cpu)
>
> Things that help:
> * make sure flow control is off
it is
> * increase transmit ring size
already at max 511 value
> * sometimes tx IRQ coalescing
yep
> Using an old SMP Opteron box for pktgen right now.
>
>> It seems timestamping is too expensive on pktgen, even for "delay 0"
>> and only one device setup (next_to_run() doesnt have to select the 'best' device)
>> We probably can improve pktgen a litle bit, or use a faster timestamping...
>
> I have a patch that might help, I haven't tested it or used it.
> It converts the pktgen calls from gettimeofday to using sched_clock()
> this saves the math overhead since pktgen only cares about comparison
> and delta's. It also prevents problems with kernel deciding clock
> source is not stable. Still need to test and review this to make
> sure pktgen only uses value on same cpu.
Well, I tried using two adapters and got more bandwidth from same CPU0, so it seems
tg3 on my machine is not able to go past 1012333pps (and BTW, bnx2 is much
slower, I dont know why...)
Configuring /proc/net/pktgen/eth3 (tg3)
Configuring /proc/net/pktgen/eth1 (bnx2)
Running... ctrl^C to stop
Done
Params: count 100000 min_pkt_size: 56 max_pkt_size: 56
frags: 0 delay: 0 clone_skb: 1000 ifname: eth3
flows: 0 flowlen: 0
queue_map_min: 0 queue_map_max: 0
dst_min: 192.168.20.120 dst_max: 192.168.20.121
src_min: src_max:
src_mac: 00:1e:0b:92:78:51 dst_mac: 00:1f:29:6b:86:15
udp_src_min: 9 udp_src_max: 9 udp_dst_min: 9 udp_dst_max: 9
src_mac_count: 0 dst_mac_count: 0
Flags:
Current:
pkts-sofar: 100000 errors: 0
started: 1251217024743446us stopped: 1251217024842450us idle: 253us
seq_num: 100001 cur_dst_mac_offset: 0 cur_src_mac_offset: 0
cur_saddr: 0x200a8c0 cur_daddr: 0x7814a8c0
cur_udp_dst: 9 cur_udp_src: 9
cur_queue_map: 0
flows: 0
Result: OK: 99004(c98751+d253) usec, 100000 (56byte,0frags)
1010060pps 452Mb/sec (452506880bps) errors: 0
Params: count 100000 min_pkt_size: 56 max_pkt_size: 56
frags: 0 delay: 0 clone_skb: 1000 ifname: eth1
flows: 0 flowlen: 0
queue_map_min: 0 queue_map_max: 0
dst_min: 192.168.20.120 dst_max: 192.168.20.121
src_min: src_max:
src_mac: 00:1e:0b:ec:d3:d2 dst_mac: 00:1f:29:6b:86:15
udp_src_min: 9 udp_src_max: 9 udp_dst_min: 9 udp_dst_max: 9
src_mac_count: 0 dst_mac_count: 0
Flags:
Current:
pkts-sofar: 100000 errors: 0
started: 1251217024743445us stopped: 1251217024888749us idle: 329us
seq_num: 100001 cur_dst_mac_offset: 0 cur_src_mac_offset: 0
cur_saddr: 0x0 cur_daddr: 0x7814a8c0
cur_udp_dst: 9 cur_udp_src: 9
cur_queue_map: 0
flows: 0
Result: OK: 145304(c144975+d329) usec, 100000 (56byte,0frags)
688212pps 308Mb/sec (308318976bps) errors: 0
07:00.0 Ethernet controller: Broadcom Corporation NetXtreme II BCM5708S Gigabit Ethernet (rev 12)
Subsystem: Hewlett-Packard Company NC373i Integrated Multifunction Gigabit Server Adapter
Flags: bus master, 66MHz, medium devsel, latency 64, IRQ 34
Memory at fa000000 (64-bit, non-prefetchable) [size=32M]
[virtual] Expansion ROM at d0000000 [disabled] [size=16K]
Capabilities: [40] PCI-X non-bridge device
Capabilities: [48] Power Management version 2
Capabilities: [50] Vital Product Data
Capabilities: [58] MSI: Enable+ Count=1/1 Maskable- 64bit+
Kernel driver in use: bnx2 (eth1)
14:04.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5715S Gigabit Ethernet (rev a3)
Subsystem: Hewlett-Packard Company NC326m PCIe Dual Port Adapter
Flags: bus master, 66MHz, medium devsel, latency 64, IRQ 35
Memory at fdff0000 (64-bit, non-prefetchable) [size=64K]
Memory at fdfe0000 (64-bit, non-prefetchable) [size=64K]
[virtual] Expansion ROM at d0200000 [disabled] [size=128K]
Capabilities: [40] PCI-X non-bridge device
Capabilities: [48] Power Management version 2
Capabilities: [50] Vital Product Data
Capabilities: [58] MSI: Enable+ Count=1/8 Maskable- 64bit+
Kernel driver in use: tg3
Kernel modules: tg3 (eth2, not used in my pktgen setup)
14:04.1 Ethernet controller: Broadcom Corporation NetXtreme BCM5715S Gigabit Ethernet (rev a3)
Subsystem: Hewlett-Packard Company NC326m PCIe Dual Port Adapter
Flags: bus master, 66MHz, medium devsel, latency 64, IRQ 37
Memory at fdfd0000 (64-bit, non-prefetchable) [size=64K]
Memory at fdfc0000 (64-bit, non-prefetchable) [size=64K]
[virtual] Expansion ROM at d0220000 [disabled] [size=128K]
Capabilities: [40] PCI-X non-bridge device
Capabilities: [48] Power Management version 2
Capabilities: [50] Vital Product Data
Capabilities: [58] MSI: Enable+ Count=1/8 Maskable- 64bit+
Kernel driver in use: tg3
Kernel modules: tg3 (eth3)
>
>> oprofile results on pktgen machine (linux 2.6.30.5) :
>> CPU: Core 2, speed 3000.08 MHz (estimated)
>> Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (Unhalted core cycles) count 100000
>> samples cum. samples % cum. % symbol name
>> 58137 58137 27.9549 27.9549 read_tsc
>> 51487 109624 24.7573 52.7122 pktgen_thread_worker
>> 33079 142703 15.9059 68.6181 getnstimeofday
>> 15694 158397 7.5464 76.1645 getCurUs
>> 11806 170203 5.6769 81.8413 do_gettimeofday
>> 5852 176055 2.8139 84.6553 kthread_should_stop
>> 5244 181299 2.5216 87.1768 kthread
>> 4181 185480 2.0104 89.1872 mwait_idle
>> 3837 189317 1.8450 91.0322 consume_skb
>> 2217 191534 1.0660 92.0983 skb_dma_unmap
>> 1599 193133 0.7689 92.8671 skb_dma_map
>> 1389 194522 0.6679 93.5350 local_bh_enable_ip
>> 1350 195872 0.6491 94.1842 nommu_map_page
>> 1086 196958 0.5222 94.7064 mix_pool_bytes_extract
>> 835 197793 0.4015 95.1079 apic_timer_interrupt
>> 774 198567 0.3722 95.4801 irq_entries_start
>> 450 199017 0.2164 95.6964 timer_stats_update_stats
>> 404 199421 0.1943 95.8907 scheduler_tick
>> 403 199824 0.1938 96.0845 find_busiest_group
>> 336 200160 0.1616 96.2460 local_bh_disable
>> 332 200492 0.1596 96.4057 rb_get_reader_page
>> 329 200821 0.1582 96.5639 ring_buffer_consume
>> 267 201088 0.1284 96.6923 add_timer_randomness
>
> The profile of pktgen will favor the tsc because it spins and looks
> at TSC during the spin. Not sure why tg3 driver overhead isn't showing up.
Sorry, for a strange reason, I have to load tg3 as a module (all other things are in static in vmlinux)
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