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From: Alireza Dabagh <alid@microsoft.com>
To: Jakub Kicinski <kuba@kernel.org>, Haiyang Zhang <haiyangz@microsoft.com>
CC: Shradha Gupta <shradhagupta@linux.microsoft.com>, Shradha Gupta
	<shradhagupta@microsoft.com>, "linux-kernel@vger.kernel.org"
	<linux-kernel@vger.kernel.org>, "linux-hyperv@vger.kernel.org"
	<linux-hyperv@vger.kernel.org>, "linux-rdma@vger.kernel.org"
	<linux-rdma@vger.kernel.org>, "netdev@vger.kernel.org"
	<netdev@vger.kernel.org>, Eric Dumazet <edumazet@google.com>, Paolo Abeni
	<pabeni@redhat.com>, Ajay Sharma <sharmaajay@microsoft.com>, Leon Romanovsky
	<leon@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, Sebastian Andrzej
 Siewior <bigeasy@linutronix.de>, KY Srinivasan <kys@microsoft.com>, Wei Liu
	<wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>, Long Li
	<longli@microsoft.com>, Michael Kelley <mikelley@microsoft.com>, Paul
 Rosswurm <paulros@microsoft.com>
Subject: RE: [EXTERNAL] Re: [PATCH] net :mana : Add per-cpu stats for MANA
 device
Thread-Topic: [EXTERNAL] Re: [PATCH] net :mana : Add per-cpu stats for MANA
 device
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Date: Thu, 14 Mar 2024 20:01:24 +0000
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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 du=
e to either NIC not handling RSS correctly, incorrect MSI-X affinity, or no=
t having enough entropy in flows.=20

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 origi=
nal inventors of RSS. So there you have it. Personally I don't think that t=
elling people "I invented the damn thing and I know what I am talking about=
" is the right way to handle this.)=20
-----Original Message-----
From: Jakub Kicinski <kuba@kernel.org>=20
Sent: Thursday, March 14, 2024 12:05 PM
To: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Shradha Gupta <shradhagupta@linux.microsoft.com>; Shradha Gupta <shradh=
agupta@microsoft.com>; linux-kernel@vger.kernel.org; linux-hyperv@vger.kern=
el.org; linux-rdma@vger.kernel.org; netdev@vger.kernel.org; Eric Dumazet <e=
dumazet@google.com>; Paolo Abeni <pabeni@redhat.com>; Ajay Sharma <sharmaaj=
ay@microsoft.com>; Leon Romanovsky <leon@kernel.org>; Thomas Gleixner <tglx=
@linutronix.de>; Sebastian Andrzej Siewior <bigeasy@linutronix.de>; KY Srin=
ivasan <kys@microsoft.com>; Wei Liu <wei.liu@kernel.org>; Dexuan Cui <decui=
@microsoft.com>; Long Li <longli@microsoft.com>; Michael Kelley <mikelley@m=
icrosoft.com>; Alireza Dabagh <alid@microsoft.com>; Paul Rosswurm <paulros@=
microsoft.com>
Subject: [EXTERNAL] Re: [PATCH] net :mana : Add per-cpu stats for MANA devi=
ce

On Thu, 14 Mar 2024 18:54:31 +0000 Haiyang Zhang wrote:
> We understand irqbalance may be a "bad idea", and recommended some=20
> customers to disable it when having problems with it... But it's still=20
> enabled by default, and we cannot let all distro vendors and custom=20
> image makers to disable the irqbalance. So, our host- networking team=20
> is eager to have per-CPU stats for analyzing CPU usage related to=20
> 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 ir=
qbalance is a user space problem.