netdev - Re: [PATCH net-next v5 0/4] Add support to do threaded napi busy poll

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Message-ID: <5fa8c9b8-527c-4392-9c9f-4e1e93ab5326@uwaterloo.ca>
Date: Mon, 28 Apr 2025 14:05:17 -0400
From: Martin Karsten <mkarsten@...terloo.ca>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>,
 Joe Damato <jdamato@...tly.com>
Cc: Samiullah Khawaja <skhawaja@...gle.com>, Jakub Kicinski
 <kuba@...nel.org>, "David S . Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
 almasrymina@...gle.com, willemb@...gle.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v5 0/4] Add support to do threaded napi busy poll

On 2025-04-28 13:59, Willem de Bruijn wrote:
> Joe Damato wrote:
>> On Mon, Apr 28, 2025 at 12:52:11PM -0400, Willem de Bruijn wrote:
>>> Martin Karsten wrote:
>>>> On 2025-04-24 16:02, Samiullah Khawaja wrote:

[snip]
>>> Users of such advanced environments can be expected to be well
>>> familiar with the cost of polling. The cost/benefit can be debated
>>> and benchmarked for individual applications. But there clearly are
>>> active uses for polling, so I think it should be an operating system
>>> facility.
>>
>> You mention users of advanced environments, but I think it's
>> important to consider the average user who is not necessarily a
>> kernel programmer.
>>
>> Will that user understand that not all apps support this? Or will
>> they think that they can simply run a few YNL commands burning CPUs at
>> 100% for apps that don't even support this thinking they are making
>> their networking faster?
> 
> Busy polling can already be configured through sysfs.

That's not the same. The existing busy-poll mechanism still needs an 
application thread. This thing will just go off and spin, whether 
there's an application or not.