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Date: Tue, 13 Feb 2024 10:04:57 -0800
From: Jakub Kicinski <kuba@kernel.org>
To: Eric Dumazet <edumazet@google.com>
Cc: Breno Leitao <leitao@debian.org>, davem@davemloft.net,
 pabeni@redhat.com, Steven Rostedt <rostedt@goodmis.org>, Masami Hiramatsu
 <mhiramat@kernel.org>, Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
 Andrew Morton <akpm@linux-foundation.org>, weiwan@google.com,
 netdev@vger.kernel.org, linux-kernel@vger.kernel.org, horms@kernel.org,
 Jonathan Corbet <corbet@lwn.net>, Randy Dunlap <rdunlap@infradead.org>,
 Bjorn Helgaas <bhelgaas@google.com>, Johannes Berg
 <johannes.berg@intel.com>, Thomas =?UTF-8?B?V2Vpw59zY2h1aA==?=
 <linux@weissschuh.net>, "open list:TRACING"
 <linux-trace-kernel@vger.kernel.org>
Subject: Re: [PATCH net-next v3] net: dqs: add NIC stall detector based on
 BQL
Message-ID: <20240213100457.6648a8e0@kernel.org>
In-Reply-To: <CANn89iLWWDjp71R7zttfTcEvZEdmcA1qo47oXkAX5DuciYvOtQ@mail.gmail.com>
References: <20240202165315.2506384-1-leitao@debian.org>
	<CANn89iLWWDjp71R7zttfTcEvZEdmcA1qo47oXkAX5DuciYvOtQ@mail.gmail.com>
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On Tue, 13 Feb 2024 14:57:49 +0100 Eric Dumazet wrote:
> Please note that adding other sysfs entries is expensive for workloads
> creating/deleting netdev and netns often.
> 
> I _think_ we should find a way for not creating
> /sys/class/net/<interface>/queues/tx-{Q}/byte_queue_limits  directory
> and files
> for non BQL enabled devices (like loopback !)

We should try, see if anyone screams. We could use IFF_NO_QUEUE, and
NETIF_F_LLTX as a proxy for "device doesn't have a real queue so BQL 
would be pointless"? Obviously better to annotate the drivers which
do have BQL support, but there's >50 of them on a quick count..