netdev - Re: Low performance Intel 10GE NIC (3.2.10) on 2.6.38 Kernel

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Date:	Thu, 07 Apr 2011 10:07:30 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Wei Gu <wei.gu@...csson.com>
Cc:	netdev <netdev@...r.kernel.org>,
	Alexander Duyck <alexander.h.duyck@...el.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Subject: Re: Low performance Intel 10GE NIC (3.2.10) on 2.6.38 Kernel

Le jeudi 07 avril 2011 à 15:22 +0800, Wei Gu a écrit :
> Hi guys,
> As I talked with Eric, that I get a very low performance on Linux 2.6.38 kernel with intel ixgbe-3.2.10 driver.
> I test different rx buff size on the Intel 10G NIC, by setting ethtool -G rx 4096.
> I get the lowest performance(~50Kpps Rx&Tx) by setting the rx==4096.
> Once I decrease the Rx to 512 (default) then I can get Max 250Kpps Rx&Tx on 1 NIC.
> 
> I was runing this test with HP DL580 4 Sock CPUs, and full memeory configuration.
> modprobe ixgbe RSS=8,8,8,8,8,8,8,8 FdirMode=0,0,0,0,0,0,0,0 Node=0,0,1,1,2,2,3,3
> Numactrl --hardware
> available: 4 nodes (0-3)
> node 0 cpus: 0 1 2 3 4 5 6 7 32 33 34 35 36 37 38 39
> node 0 size: 65525 MB
> node 0 free: 63053 MB
> node 1 cpus: 8 9 10 11 12 13 14 15 40 41 42 43 44 45 46 47
> node 1 size: 65536 MB
> node 1 free: 63388 MB
> node 2 cpus: 16 17 18 19 20 21 22 23 48 49 50 51 52 53 54 55
> node 2 size: 65536 MB
> node 2 free: 63344 MB
> node 3 cpus: 24 25 26 27 28 29 30 31 56 57 58 59 60 61 62 63
> node 3 size: 65535 MB
> node 3 free: 63376 MB
> 
> Then I binding the eth10's rx and tx's IRQs to core "24 25 26 27 28 29 30 31", one by one, which means 1 rx and 1 tx was share 1 core.
> 
> 
> I did the same test on 2.6.32 kernel, I can get >2.5M tx&rx with the same setup on RHEL6(2.6.32) Linux. But never reach 10.000.000 rx&tx on a single NIC:)
> 
> I also test the 2.6.38 shipped intel ixgbe driver It has the same problem.
> 
> This is a perf record with linux shipped ixgbe driver, looks it has a very high irq/s rate. And the softirq was busy on alloc_iova
> 
> 
> PerfTop:  512417 irqs/sec  kernel:91.3%  exact:  0.0% [1000Hz cpu-clock-msecs],  (all, 64 CPUs)
> ------------------------------------------------------------------------------------------------------------------------------------------------------
> -      0.82%     ksoftirqd/24  [kernel.kallsyms]          [k] _raw_spin_unlock_irqrestore
> \u2592   - _raw_spin_unlock_irqrestore
> \u2592      - 44.27% alloc_iova
> \u2592           intel_alloc_iova
> \u2592           __intel_map_single
> \u2592           intel_map_page
> \u2592         - ixgbe_init_interrupt_scheme
> \u2592            - 59.97% ixgbe_alloc_rx_buffers
> \u2592                 ixgbe_clean_rx_irq
> \u2592                 0xffffffffa033a5
> \u2592                 net_rx_action
> u2592                 __do_softirq
> \u2592               + call_softirq
> \u2592            - 40.03% ixgbe_change_mtu
> \u2592                 ixgbe_change_mtu
> \u2592                 dev_hard_start_xmit
> \u2592                 sch_direct_xmit
> \u2592                 dev_queue_xmit
> \u2592                 vlan_dev_hard_start_xmit
> \u2592                 hook_func
> \u2592                 nf_iterate
> \u2592                nf_hook_slow
> \u2592                 NF_HOOK.clone.1
> \u2592                 ip_rcv
> \u2592                 __netif_receive_skb
> \u2592                 __netif_receive_skb
> \u2592                 netif_receive_skb
> \u2592                 napi_skb_finish
> \u2592                 napi_gro_receive
> \u2592                 ixgbe_clean_rx_irq
> \u2592                 0xffffffffa033a5
> \u2592                 net_rx_action
> \u2592                 __do_softirq
> \u2592               + call_softirq
> \u2592      + 35.85% find_iova
> \u2592      + 19.44% add_unmap
> 
> 
> Thanks
> WeiGu

What about using the driver as provided in 2.6.38 ?

No custom module parameter, only play with irq affinities

Say you have 64 queues but want only 8 cpus (24 -> 31) receiving trafic

for i in `seq 0 7`
do
 echo 01000000 >/proc/irq/*/eth1-fp-$i/../smp_affinity
done

for i in `seq 8 15`
do
 echo 02000000 >/proc/irq/*/eth1-fp-$i/../smp_affinity
done

...

for i in `seq 56 63`
do
 echo 80000000 >/proc/irq/*/eth1-fp-$i/../smp_affinity
done


Why is ixgbe_change_mtu() seen on your profile ?
Its damn expensive, since it must call ixgbe_reinit_locked()

Are you using a custom code in kernel ?



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