linux-kernel - Re: Pure polling mode for netdevices

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Message-ID: <1477075306.7065.86.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Fri, 21 Oct 2016 11:41:46 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Zach Brown <zach.brown@...com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Pure polling mode for netdevices

On Fri, 2016-10-21 at 13:03 -0500, Zach Brown wrote:
> Is there a way to get NAPI to poll all the time?
> Or just any way to get netdevices to use only polling and no interrupts?
> 
> We have some rt targets where the jitter can be improved by disabling
> interrupts and using just polling. In these cases we're okay with the
> performance downsides that come with polling.
> 
> In particular we already have an implementation for the cadence macb driver
> that does only polling mode and have verified that it improves the
> jitter.
> 
> We're hoping for a more general existing solution or at the very least a
> solution that would be accepted upstream. Any thoughts?

This is not yet done, although you could use busy poll infrastructure to
get this without a kernel change.

Open as many TCP flows are necessary to traverse all the queues you care
about, then loop on recvmsg() to trigger NAPI polling.