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From: Robert Watson <rwatson@FreeBSD.org>
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To: George Neville-Neil <gnn@neville-neil.com>
Subject: Re: Enabling VIMAGE in GENERIC
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Cc: Craig Rodrigues <rodrigc@FreeBSD.org>,
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On Mon, 1 Dec 2014, George Neville-Neil wrote:

> On a slight tangent.  I ran VIMAGE kernels vs. non VIMAGE kernels for both a 
> VANILLA kernel and a PF kernel (PF on but no rules) as a quick smoke test 
> today.  The raw forwarding performance was unchanged between kernels with 
> and without VIMAGE on a 10G based system in the Sentex lab (lion1).  I will 
> be doing a bit more work in this area and will then put up some results in 
> my netperf github repo.

Was this a CPU-bound or network-bound workload?  In general, I'd expect VIMAGE 
to have a modest overhead for most measurable workloads .. unless you are 
CPU-bound, in which case per-packet processing overheads might become 
(potentially) quite visible.  They will also be more visible on simpler 
pipelines and with less cache-rich designs -- e.g., SoCs of various sorts. 
Doing a bit of CPU-bound networking on a modest ARM core might show off the 
effects better.

Robert