netdev - Re: Interpreting perf stat on netperf and netserver

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Date:	Thu, 19 Jan 2012 11:26:34 +0100
From:	Jean-Michel Hautbois <jhautbois@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: Interpreting perf stat on netperf and netserver

2012/1/19 Eric Dumazet <eric.dumazet@...il.com>:
> Le mercredi 18 janvier 2012 à 12:33 +0100, Jean-Michel Hautbois a
> écrit :
>
>> The be2net driver seems to have difficulties woth IRQ affinity also,
>> because it always uses CPU0 even if the affinity is 0-23 !
>> netperf result is quite good, and perf top shows :
>>    PerfTop:     689 irqs/sec  kernel:99.6% us: 0.3% guest kernel: 0.0%
>> guest us: 0.0% exact:  0.0% [1000Hz cycles],  (all, 24 CPUs)
>> ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>>
>>     29.28%  [kernel]          [k] csum_partial
>>      8.46%  [kernel]          [k] copy_user_generic_string
>>      3.70%  [be2net]          [k] be_poll_rx
>>      3.08%  [be2net]          [k] event_handle
>>      2.37%  [kernel]          [k] irq_entries_start
>>      2.21%  [be2net]          [k] be_rx_compl_get
>>      1.65%  [be2net]          [k] be_post_rx_frags
>>      1.64%  [kernel]          [k] __napi_complete
>>      1.50%  [kernel]          [k] ip_defrag
>>      1.35%  [kernel]          [k] put_page
>>      1.34%  [kernel]          [k] get_page_from_freelist
>>      1.29%  [kernel]          [k] __netif_receive_skb
>>      1.16%  [kernel]          [k] __alloc_pages_nodemask
>>      1.14%  [kernel]          [k] debug_smp_processor_id
>>      1.08%  [kernel]          [k] add_preempt_count
>>      1.06%  [kernel]          [k] sub_preempt_count
>>      1.03%  [be2net]          [k] get_rx_page_info
>>      1.01%  [kernel]          [k] alloc_pages_current
>>
>> Checksum calculation seems quite complex :).
>
> UDP with fragments... I guess... but cant see this in the perf top
> output ;)
>
> What bandwidth do you get for this cpu load ?

Yes, this was UDP fragmentation :). I had 6800Mbps for a theoretical
limit of 7000Mbps (Flex 10Gbps system).

JM
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