netdev - Re: [PATCH net-next v6] Add support to set napi threaded for individual napi

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Message-ID: <20250502191548.559cc416@kernel.org>
Date: Fri, 2 May 2025 19:15:48 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Joe Damato <jdamato@...tly.com>
Cc: Samiullah Khawaja <skhawaja@...gle.com>, "David S . Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni
 <pabeni@...hat.com>, almasrymina@...gle.com, willemb@...gle.com,
 mkarsten@...terloo.ca, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v6] Add support to set napi threaded for
 individual napi

On Wed, 30 Apr 2025 11:11:03 -0700 Joe Damato wrote:
>   > We should check the discussions we had when threaded NAPI was added.
>   > I feel nothing was exposed in terms of observability so leaving the
>   > thread running didn't seem all that bad back then. Stopping the NAPI
>   > polling safely is not entirely trivial, we'd need to somehow grab
>   > the SCHED bit like busy polling does, and then re-schedule.
>   > Or have the thread figure out that it's done and exit.  
>   
>   Actually, we ended up adding the explicit ownership bits so it may not
>   be all that hard any more.. Worth trying.
> 
> So based on all of the messages in the v5 and in the past, it seems pretty
> clear to me that this needs to be fixed.

Joe is right, sorry for not replying earlier.
Let's try to stop / start the thread on SET immediately.

IIRC there was also a suggestion to defer start / stop to
napi_enable() if NAPI is not enabled -- that's not needed.