netdev - Re: [RFC] bnx2x: Insane RX rings

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Date:	Thu, 09 Sep 2010 23:21:01 +0200
From:	Krzysztof Olędzki <ole@....pl>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	netdev <netdev@...r.kernel.org>,
	Eilon Greenstein <eilong@...adcom.com>
Subject: Re: [RFC] bnx2x: Insane RX rings

On 2010-09-09 22:45, Eric Dumazet wrote:
> So I have a small dev machine, 4GB of ram,
> a dual E5540 cpu (quad core, 2 threads per core),
> so a total of 16 threads.
>
> Two ethernet ports, eth0 and eth1,
>
> 02:00.0 Ethernet controller: Broadcom Corporation NetXtreme II BCM57711E 10Gigabit PCIe
> 02:00.1 Ethernet controller: Broadcom Corporation NetXtreme II BCM57711E 10Gigabit PCIe
>
> bnx2x 0000:02:00.0: eth0: using MSI-X  IRQs: sp 68  fp[0] 69 ... fp[15] 84
> bnx2x 0000:02:00.1: eth1: using MSI-X  IRQs: sp 85  fp[0] 86 ... fp[15] 101
>
>
> Default configuration :
>
> ethtool -g eth0
> Ring parameters for eth0:
> Pre-set maximums:
> RX:		4078
> RX Mini:	0
> RX Jumbo:	0
> TX:		4078
> Current hardware settings:
> RX:		4078
> RX Mini:	0
> RX Jumbo:	0
> TX:		4078
>
> Problem is : With 16 RX queues per device , thats 4078*16*2Kbytes per
> ethernet port.
>
> Total :
>
> skbuff_head_cache 130747 131025    256   15    1 : tunables  120   60    8 : slabdata   8735   8735     40
> size-2048         130866 130888   2048    2    1 : tunables   24   12    8 : slabdata  65444  65444     28
>
> Thats about 300 Mbytes of memory, just in case some network trafic will occur.
>
> Lets do something about that ?

Yep, it is ~8MB per queue, not so much alone, but a lot together. For 
this reason I use something like bnx2.num_queues=2 on servers where I 
don't need much CPU power for network workload.

Best regards,

			Krzysztof Olędzki
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