[P4-discuss] Energy efficient programmable switch

[Debobroto Das]

Hello everyone, 

I was looking through some of the features of P4 enabled switches. But,

I have not seen anything regarding energy-efficient features. 

Is it due to some kind of architectural constraints that energy efficient features are not available in programmable switches? Or I am missing something. 

[Andy Fingerhut]

Can you give an example or two of the kinds of energy efficient features you were looking for?  Or that exist in other categories of devices that you were wishing to find?

e.g. dynamic frequency scaling?  auto-shutdown of Ethernet links when they aren't in use?  Something else?

Andy

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[Debobroto Das]

Most these 2 you have mentioned a) dynamic frequency scaling b)  auto-shutdown of Ethernet links when they aren't in use.

Additionally looking for TCAM and memory blocks. If for a specific program some of these resources are not used, is it possible to turn them off? 

[Andy Fingerhut]

Vendors of all computer hardware are pushed by their customers to be energy efficient, where possible.

The P4 language itself doesn't really have much to say about such things, because the kinds of energy-saving features described are not really visible to, or controlled by, the things that control how an individual packet is processed.

If you get detailed enough data sheets of switch/NIC products, and/or talk to a sales rep about it, they can tell you what features a particular device has.  I am not claiming that all devices have all of the features you want, but at least some products likely do.

Andy

[Debobroto Das]

I understand that, P4 do not have much to do with energy saving features. I haven't found too many data sheets openly available. Or at least I can't access them. I was concerned about is there any specific architectural reason that can bar from turning a port off. 

For example, assume 4 pipeline for serving a 12.8 tbps switch with per pipeline managing 16 ports. Now, if 16 ports are turned off, I can assume that if all of them were served by a single pipeline. The pipeline itself can be turned off. But if the 16 ports are not served by same pipeline what can be the result. 

[Andy Fingerhut]

The level of detail of features you are asking about are often not put into public data sheets, but only shared with potential customers that the vendors believe are serious about providing enough business to share that information with.  The newer and more cutting-edge a product is in high tech, the more likely that is to be the case.  The more mass market and/or older the technology is, the more likely that more details have become public.

Turning off power for Ethernet ports, independently of each other, seems to me like something that should be independent of internal hardware architecture, and provides a lot of bang for the buck in terms of supporting it, so is probably among the more commonly supported options.

How switch ASICs are organized internally can vary significantly from one vendor's products to another, and even between different products from the same vendor sometimes.

In your particular example, wondering whether an entire pipe can be powered off, such a feature would be an extra level of engineering effort to implement, and might not be worth the extra time and care required.  (I haven't done such an analysis of the effort required, nor how much power it would save -- I am speaking in generalities of the kinds of issues a hardware architect would ask before implementing such a feature).

Andy

[Debobroto Das]

Thanks a lot for the information.