netdev - Re: [EXTERNAL] Re: [PATCH] net :mana : Add per-cpu stats for MANA device

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Date: Tue, 2 Apr 2024 22:43:51 -0700
From: Shradha Gupta <shradhagupta@...ux.microsoft.com>
To: Alireza Dabagh <alid@...rosoft.com>
Cc: Jakub Kicinski <kuba@...nel.org>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Shradha Gupta <shradhagupta@...rosoft.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	Ajay Sharma <sharmaajay@...rosoft.com>,
	Leon Romanovsky <leon@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	KY Srinivasan <kys@...rosoft.com>, Wei Liu <wei.liu@...nel.org>,
	Dexuan Cui <decui@...rosoft.com>, Long Li <longli@...rosoft.com>,
	Michael Kelley <mikelley@...rosoft.com>,
	Paul Rosswurm <paulros@...rosoft.com>
Subject: Re: [EXTERNAL] Re: [PATCH] net :mana : Add per-cpu stats for MANA
 device

Hi all,
I have a newer version of this patch with netlink implementation ready, to support the usecase of per-cpu stats for RSS handling and imbalance investigations. Please let me know if we can proceed with that.

Thanks and regards,
Shradha.

On Thu, Mar 14, 2024 at 08:01:24PM +0000, Alireza Dabagh wrote:
> Per processor network stats have been supported on netvsc and Mellanox NICs for years. They are also supported on Windows.
> 
> I routinely use these stats to rule in/out the issues with RSS imbalance due to either NIC not handling RSS correctly, incorrect MSI-X affinity, or not having enough entropy in flows. 
> 
> And yes, I perfectly understand that there are cases that packets received on processor x are processed (in tcp/ip stack) on processor y. But in many cases, there is a correlation between individual processor utilization and the processor where these packets are received on by the NIC.
> 
> -thanks, ali
> (some suggested that I do mention on this thread that I am one of the original inventors of RSS. So there you have it. Personally I don't think that telling people "I invented the damn thing and I know what I am talking about" is the right way to handle this.) 
> -----Original Message-----
> From: Jakub Kicinski <kuba@...nel.org> 
> Sent: Thursday, March 14, 2024 12:05 PM
> To: Haiyang Zhang <haiyangz@...rosoft.com>
> Cc: Shradha Gupta <shradhagupta@...ux.microsoft.com>; Shradha Gupta <shradhagupta@...rosoft.com>; linux-kernel@...r.kernel.org; linux-hyperv@...r.kernel.org; linux-rdma@...r.kernel.org; netdev@...r.kernel.org; Eric Dumazet <edumazet@...gle.com>; Paolo Abeni <pabeni@...hat.com>; Ajay Sharma <sharmaajay@...rosoft.com>; Leon Romanovsky <leon@...nel.org>; Thomas Gleixner <tglx@...utronix.de>; Sebastian Andrzej Siewior <bigeasy@...utronix.de>; KY Srinivasan <kys@...rosoft.com>; Wei Liu <wei.liu@...nel.org>; Dexuan Cui <decui@...rosoft.com>; Long Li <longli@...rosoft.com>; Michael Kelley <mikelley@...rosoft.com>; Alireza Dabagh <alid@...rosoft.com>; Paul Rosswurm <paulros@...rosoft.com>
> Subject: [EXTERNAL] Re: [PATCH] net :mana : Add per-cpu stats for MANA device
> 
> On Thu, 14 Mar 2024 18:54:31 +0000 Haiyang Zhang wrote:
> > We understand irqbalance may be a "bad idea", and recommended some 
> > customers to disable it when having problems with it... But it's still 
> > enabled by default, and we cannot let all distro vendors and custom 
> > image makers to disable the irqbalance. So, our host- networking team 
> > is eager to have per-CPU stats for analyzing CPU usage related to 
> > irqbalance or other issues.
> 
> You need a use case to get the stats upstream.
> "CPU usage related to irqbalance or other issues" is both too vague, and irqbalance is a user space problem.