netdev - Re: [RFC PATCH 00/17] virtual-bus

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Date:	Thu, 02 Apr 2009 09:03:21 -0400
From:	Gregory Haskins <ghaskins@...ell.com>
To:	Avi Kivity <avi@...hat.com>
CC:	Herbert Xu <herbert@...dor.apana.org.au>, anthony@...emonkey.ws,
	andi@...stfloor.org, linux-kernel@...r.kernel.org, agraf@...e.de,
	pmullaney@...ell.com, pmorreale@...ell.com, rusty@...tcorp.com.au,
	netdev@...r.kernel.org, kvm@...r.kernel.org,
	Mark McLoughlin <markmc@...hat.com>
Subject: Re: [RFC PATCH 00/17] virtual-bus

Avi Kivity wrote:
> Gregory Haskins wrote:
>
>  
>
>>> It's more of a "schedule and forget" which I think brings you the
>>> win.  The host disables notifications and schedules the actual tx work
>>> (rx from the host's perspective).  So now the guest and host continue
>>> producing and consuming packets in parallel.  So long as the guest is
>>> faster (due to the host being throttled?), notifications continue to
>>> be disabled.
>>>     
>> Yep, when the "producer::consumer" ratio is > 1, we mitigate
>> signaling. When its < 1, we signal roughly once per packet.
>>
>>  
>>> If you changed your rx_isr() to process the packets immediately
>>> instead of scheduling, I think throughput would drop dramatically.
>>>     
>> Right, that is the point. :) This is that "soft asic" thing I was
>> talking about yesterday.
>>   
>
> But all that has nothing to do with where the code lives, in the
> kernel or userspace.

Agreed, but note Ive already stated that some of my boost is likely from
in-kernel, while others are unrelated design elements such as the
"soft-asic" approach (you guys dont read my 10 page emails, do you? ;). 
I don't deny that some of my ideas could be used in userspace as well
(Credit if used would be appreciated :).

-Greg



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