netdev - Re: ixgbe question

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Date:	Mon, 23 Nov 2009 15:38:06 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jesper Dangaard Brouer <hawk@...u.dk>
CC:	Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@...el.com>,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: ixgbe question

Jesper Dangaard Brouer a écrit :

> How is your smp_affinity mask's set?
> 
> grep . /proc/irq/*/fiber1-*/../smp_affinity

First, I tried default affinities (ffff)

Then I tried irqbalance... no more success.

Driver seems to try to handle all queues on one cpu on low trafic,
and possibly dynamically switches to a multi-cpu mode,
but as all interrupts are masked, we stay in 
a NAPI context handling all queues.

And we let one cpu in flood/drops mode.




> 
> 
>> But only one CPU (CPU1) had a softirq running, 100%, and many frames
>> were dropped
> 
> Just a hint, I use 'ethtool -S fiber1' to see how the packets gets
> distributed across the rx and tx queues.

They are correctly distributed

     rx_queue_0_packets: 14119644
     rx_queue_0_bytes: 847178640
     rx_queue_1_packets: 14126315
     rx_queue_1_bytes: 847578900
     rx_queue_2_packets: 14115249
     rx_queue_2_bytes: 846914940
     rx_queue_3_packets: 14118146
     rx_queue_3_bytes: 847088760
     rx_queue_4_packets: 14130869
     rx_queue_4_bytes: 847853268
     rx_queue_5_packets: 14112239
     rx_queue_5_bytes: 846734340
     rx_queue_6_packets: 14128425
     rx_queue_6_bytes: 847705500
     rx_queue_7_packets: 14110587
     rx_queue_7_bytes: 846635220
     rx_queue_8_packets: 14117350
     rx_queue_8_bytes: 847041000
     rx_queue_9_packets: 14125992
     rx_queue_9_bytes: 847559520
     rx_queue_10_packets: 14121732
     rx_queue_10_bytes: 847303920
     rx_queue_11_packets: 14120997
     rx_queue_11_bytes: 847259820
     rx_queue_12_packets: 14125576
     rx_queue_12_bytes: 847535854
     rx_queue_13_packets: 14118512
     rx_queue_13_bytes: 847110720
     rx_queue_14_packets: 14118348
     rx_queue_14_bytes: 847100880
     rx_queue_15_packets: 14118647
     rx_queue_15_bytes: 847118820



> 
> 
> 
>> CLONE_SKB="clone_skb 15"
> 
> Be careful with to high clone, as my experience is it will send a burst
> of clone_skb packets before the packet gets randomized again.

Yes, but 15 should be ok with 10Gb link  :)

Thanks
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