netdev - Re: [RFC net-next 1/2] page_pool: allow caching from safely localized NAPI

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Date:   Mon, 3 Apr 2023 18:45:45 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Yunsheng Lin <linyunsheng@...wei.com>
Cc:     <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <edumazet@...gle.com>, <pabeni@...hat.com>, <hawk@...nel.org>,
        <ilias.apalodimas@...aro.org>
Subject: Re: [RFC net-next 1/2] page_pool: allow caching from safely
 localized NAPI

On Tue, 4 Apr 2023 08:53:36 +0800 Yunsheng Lin wrote:
> I wonder if we can make this more generic by adding the skb to per napi
> list instead of sd->defer_list, so that we can always use NAPI kicking to
> flush skb as net_tx_action() done for sd->completion_queue instead of
> softirq kicking?
> 
> And it seems we know which napi binds to a specific socket through
> busypoll mechanism, we can reuse that to release a skb to the napi
> bound to that socket?

Seems doable. My thinking was to first see how well the simpler scheme
performs with production workloads because it should have no downsides.
Tracking real NAPI pointers per socket and extra RCU sync to manage
per-NAPI defer queues may have perf cost.