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

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Message-ID:
 <CH2PR21MB1480D4AE8D329B5F00B184A7CA272@CH2PR21MB1480.namprd21.prod.outlook.com>
Date: Fri, 8 Mar 2024 19:43:57 +0000
From: Haiyang Zhang <haiyangz@...rosoft.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: Shradha Gupta <shradhagupta@...ux.microsoft.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>, Paul Rosswurm <paulros@...rosoft.com>, Alireza Dabagh
	<alid@...rosoft.com>, Sharath George John <sgeorgejohn@...rosoft.com>
Subject: RE: [PATCH] net :mana : Add per-cpu stats for MANA device



> -----Original Message-----
> From: Jakub Kicinski <kuba@...nel.org>
> Sent: Friday, March 8, 2024 2:23 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>
> Subject: Re: [PATCH] net :mana : Add per-cpu stats for MANA device
> 
> On Fri, 8 Mar 2024 18:51:58 +0000 Haiyang Zhang wrote:
> > > Dynamic is a bit of an exaggeration, right? On a well-configured
> system
> > > each CPU should use a single queue assigned thru XPS. And for manual
> > > debug bpftrace should serve the purpose quite well.
> >
> > Some programs, like irqbalancer can dynamically change the CPU
> affinity,
> > so we want to add the per-CPU counters for better understanding of the
> CPU
> > usage.
> 
> Do you have experimental data showing this making a difference
> in production?
Shradha, could you please add some data before / after enabling irqbalancer 
which changes cpu affinity?

> 
> Seems unlikely, but if it does work we should enable it for all
> devices, no driver by driver.
There are some existing drivers, like mlx, rmnet, netvsc, etc. using percpu 
counters. Are you suggesting we add a common API for all drivers?

Thanks,
- Haiyang