netdev - Re: [PATCH v3 4/4] net: mana: Allocate MSI-X vectors dynamically

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Message-ID: <aCTN4yfHBsJGXvnB@yury>
Date: Wed, 14 May 2025 13:07:47 -0400
From: Yury Norov <yury.norov@...il.com>
To: Michael Kelley <mhklinux@...look.com>
Cc: Shradha Gupta <shradhagupta@...ux.microsoft.com>,
	Dexuan Cui <decui@...rosoft.com>, Wei Liu <wei.liu@...nel.org>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Konstantin Taranov <kotaranov@...rosoft.com>,
	Simon Horman <horms@...nel.org>, Leon Romanovsky <leon@...nel.org>,
	Maxim Levitsky <mlevitsk@...hat.com>,
	Erni Sri Satya Vennela <ernis@...ux.microsoft.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Nipun Gupta <nipun.gupta@....com>, Jason Gunthorpe <jgg@...pe.ca>,
	Jonathan Cameron <Jonathan.Cameron@...ei.com>,
	Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Kevin Tian <kevin.tian@...el.com>, Long Li <longli@...rosoft.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Bjorn Helgaas <bhelgaas@...gle.com>, Rob Herring <robh@...nel.org>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Krzysztof Wilczy�~Dski <kw@...ux.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
	Paul Rosswurm <paulros@...rosoft.com>,
	Shradha Gupta <shradhagupta@...rosoft.com>
Subject: Re: [PATCH v3 4/4] net: mana: Allocate MSI-X vectors dynamically

On Wed, May 14, 2025 at 05:04:03AM +0000, Michael Kelley wrote:
> From: Shradha Gupta <shradhagupta@...ux.microsoft.com> Sent: Friday, May 9, 2025 3:14 AM
> > 
> > Currently, the MANA driver allocates MSI-X vectors statically based on
> > MANA_MAX_NUM_QUEUES and num_online_cpus() values and in some cases ends
> > up allocating more vectors than it needs. This is because, by this time
> > we do not have a HW channel and do not know how many IRQs should be
> > allocated.
> > 
> > To avoid this, we allocate 1 MSI-X vector during the creation of HWC and
> > after getting the value supported by hardware, dynamically add the
> > remaining MSI-X vectors.
> 
> After this patch is applied, there are two functions for setting up IRQs:
> 1. mana_gd_setup_dyn_irqs()
> 2. mana_gd_setup_irqs()
> 
> #1 is about 78 lines of code and comments, while #2 is about 103 lines of
> code and comments. But the two functions have a lot of commonality,
> and that amount of commonality raises a red flag for me.
> 
> Have you looked at parameterizing things so a single function can serve
> both purposes? I haven't worked through all the details, but at first
> glance it looks very feasible, and without introducing unreasonable
> messiness. Saving 70 to 80 lines of fairly duplicative code is worth a bit
> of effort.
> 
> I have some other comments on the code. But if those two functions can
> be combined, I'd rather re-review the result before adding comments that
> may become irrelevant due to the restructuring.
> 
> Michael

On previous iteration I already mentioned that this patch is too big,
doesn't do exactly one thing and should be split to become a reviewable 
change. Shradha split-out the irq_setup() piece, and your review proves
that splitting helps to reviewability.

The rest of the change is still a mess. I agree that the functions you
mention likely duplicate each other. But overall, this patch bomb is
above my ability to review. Fortunately, I don't have to.

Thanks,
Yury