netdev - RE: [RFC] ethtool bandwidth per-queue commands

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Date:	Wed, 20 Jul 2016 20:51:01 +0000
From:	"Liang, Kan" <kan.liang@...el.com>
To:	ivan <khorivan@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:	David Miller <davem@...emloft.net>
Subject: RE: [RFC] ethtool bandwidth per-queue commands



> 
> Hi everyone.
> 
> The ethtool interface has ETHTOOL_PERQUEUE command that is used to
> read/set per-queue parameters for multiqueue Ethernet devices.
> 
> I want to apply additional per-queue commands like per-queue bandwidth
> and per-queue number of descriptors (like number of rings).
> 
> Currently only ETHTOOL_G/SCOALESCE sub commands are added for per-
> queue interface (but I haven't seen counterpart for ethtool util).
> 
> Using ETHTOOL_G/SCOALESCE per-queue command as an example, I'm
> going to add 2 additional and 2 known commands for ethtool per-queue
> interface:
> 
> ETHTOOL_G/SBANDWIDTH     /* Get/Set ethtool per queue bandwidth.
> Bandwidth can be set with % or absolute in Mb/s */
> 
> ETHTOOL_G/SRINGPARAM     /* is going to be used to control number of
> descriptors per queue in my driver */
> 
> It's not clear how PERQUEUE command splits rx and tx queues, as they can
> have different enumeration and different parameters.
> 
> Actually, there are several questions:
> - how to split enumeration of rx / tx queues in per queue command,
>    as it uses linear bitmap to mirror affected channels.
> - where is ethtool util counterpart for per queue command?
> - is it correct way to use ethtool to configure h/w shaper?
> 

I once submitted a patch series for ethtool to do per-queue setting.
https://www.mail-archive.com/netdev%40vger.kernel.org/msg110727.html
But it's not merged. Because I didn't have a chance to address Ben's
comments yet.
https://www.mail-archive.com/netdev%40vger.kernel.org/msg116630.html

I guess you may extend the ethtool patch series, and use it to verify your
kernel changes.

Kan


> In my case, by default, multi queue h/w shaper is working in priority mode.
> The setting of bandwidth for queues can be used to switch shaper to
> throughput aware mode when every queue can be bandwidth limited.
> 
> --
> Regards,
> Ivan Khoronzhuk