netdev - Re: [PATCH net-next] docs: networking: document NAPI

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Message-ID: <20230315155202.2bba7e20@hermes.local>
Date:   Wed, 15 Mar 2023 15:52:02 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
        pabeni@...hat.com, jesse.brandeburg@...el.com,
        anthony.l.nguyen@...el.com, corbet@....net,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH net-next] docs: networking: document NAPI

On Wed, 15 Mar 2023 15:30:44 -0700
Jakub Kicinski <kuba@...nel.org> wrote:

> Add basic documentation about NAPI. We can stop linking to the ancient
> doc on the LF wiki.
> 
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> ---
> CC: jesse.brandeburg@...el.com
> CC: anthony.l.nguyen@...el.com
> CC: corbet@....net
> CC: linux-doc@...r.kernel.org

The one thing missing, is how to handle level vs edge triggered interrupts.
For level triggered interrupts, the re-enable is inherently not racy.
I.e re-enabling interrupt when packet is present will cause an interrupt.
But for devices with edge triggered interrupts, it is often necessary to
poll and manually schedule again. Older documentation referred to this
as the "rotten packet" problem.

Maybe this is no longer a problem for drivers?
Or maybe all new hardware uses PCI MSI and is level triggered?