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Message-ID: <1302152327.2701.50.camel@edumazet-laptop>
Date:	Thu, 07 Apr 2011 06:58:47 +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: Question on "net: allocate skbs on local node"

Le jeudi 07 avril 2011 à 10:16 +0800, Wei Gu a écrit :
> Hi Eric,
> Testing with ixgbe Linux 2.6.38 driver:
> We have a little better thruput figure with this driver, but it looks
> not scalling at all, I always stressed one CPU core/24.
> And when look the perf report for ksoftirqd/24, the most cost function
> is still "_raw_spin_unlock_irqstore" and the IRQ/s is huge, it's
> somehow conflicts with desgin of NAPI. On linux 2.6.32 while the CPU
> was stressed the IRQ will descreased while the NAPI will running much
> on the polling mode. I don't know why on 2.6.38 the IRQ was keep
> increasing.


CC netdev and Intel guys, since they said it should not happen (TM)

IF you dont use DCA (make sure ioatdma module is not loaded), how comes
alloc_iova() is called at all ?

IF you use DCA, how comes its called, since the same CPU serves a given
interrupt ?



>  
> CONFIG_TICK_ONESHOT=y
> CONFIG_NO_HZ=y
>  
> 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
>  


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