Re: [RFC v2: Patch 1/3] net: hand off skb list to other cpu to submit to upper layer

[Tom Herbert]

On Fri, Mar 13, 2009 at 7:19 PM, David Miller <davem@xxxxxxxxxxxxx> wrote:
> From: Tom Herbert <therbert@xxxxxxxxxx>
> Date: Fri, 13 Mar 2009 17:24:10 -0700
>
>> Enabling HW multi-queue has somewhat higher CPU
>> utilization though, the extra device interrupt load is not coming for
>> free.  We actually use the HW multi-queue in conjunction with our
>> software steering to get maximum pps (about 20% more).
>
> This is a non-intuitive observation.  Using HW multiqueue should be
> cheaper than doing it in software, right?
>

I suppose it may be counter-intuitive, but I am not making a general
claim.  I would only suggest that these software hacks could be a very
good approximation or substitute for hardware functionality.  This is
a generic way to get more performance out of deficient or lower end
NICs.
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