netdev - Re: [RFC net-next 0/7] Provide an ism layer

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Message-ID: <20250118153154.GI89233@linux.alibaba.com>
Date: Sat, 18 Jan 2025 23:31:54 +0800
From: Dust Li <dust.li@...ux.alibaba.com>
To: Niklas Schnelle <schnelle@...ux.ibm.com>,
	Alexandra Winter <wintera@...ux.ibm.com>,
	Julian Ruess <julianr@...ux.ibm.com>,
	Wenjia Zhang <wenjia@...ux.ibm.com>,
	Jan Karcher <jaka@...ux.ibm.com>, Gerd Bayer <gbayer@...ux.ibm.com>,
	Halil Pasic <pasic@...ux.ibm.com>,
	"D. Wythe" <alibuda@...ux.alibaba.com>,
	Tony Lu <tonylu@...ux.alibaba.com>,
	Wen Gu <guwen@...ux.alibaba.com>,
	Peter Oberparleiter <oberpar@...ux.ibm.com>,
	David Miller <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Andrew Lunn <andrew+netdev@...n.ch>
Cc: Thorsten Winkler <twinkler@...ux.ibm.com>, netdev@...r.kernel.org,
	linux-s390@...r.kernel.org, Heiko Carstens <hca@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	Sven Schnelle <svens@...ux.ibm.com>,
	Simon Horman <horms@...nel.org>
Subject: Re: [RFC net-next 0/7] Provide an ism layer

On 2025-01-17 11:38:39, Niklas Schnelle wrote:
>On Fri, 2025-01-17 at 10:13 +0800, Dust Li wrote:
>> > 
>---8<---
>> > Here are some of my thoughts on the matter:
>> > > > 
>> > > > Naming and Structure: I suggest we refer to it as SHD (Shared Memory
>> > > > Device) instead of ISM (Internal Shared Memory). 
>> > 
>> > 
>> > So where does the 'H' come from? If you want to call it Shared Memory _D_evice?
>> 
>> Oh, I was trying to refer to SHM(Share memory file in the userspace, see man
>> shm_open(3)). SMD is also OK.
>> 
>> > 
>> > 
>> > To my knowledge, a
>> > > > "Shared Memory Device" better encapsulates the functionality we're
>> > > > aiming to implement. 
>> > 
>> > 
>> > Could you explain why that would be better?
>> > 'Internal Shared Memory' is supposed to be a bit of a counterpart to the
>> > Remote 'R' in RoCE. Not the greatest name, but it is used already by our ISM
>> > devices and by ism_loopback. So what is the benefit in changing it?
>> 
>> I believe that if we are going to separate and refine the code, and add
>> a common subsystem, we should choose the most appropriate name.
>> 
>> In my opinion, "ISM" doesn’t quite capture what the device provides.
>> Since we’re adding a "Device" that enables different entities (such as
>> processes or VMs) to perform shared memory communication, I think a more
>> fitting name would be better. If you have any alternative suggestions,
>> I’m open to them.
>
>I kept thinking about this a bit and I'd like to propose yet another
>name for this group of devices: Memory Communication Devices (MCD)
>
>One important point I see is that there is a bit of a misnomer in the
>existing ISM name in that our ISM device does in fact *not* share
>memory in the common sense of the "shared memory" wording. Instead it
>copies data between partitions of memory that share a common
>cache/memory hierarchy while not sharing the memory itself. loopback-
>ism and a possibly future virtio-ism on the other hand would share
>memory in the "shared memory" sense. Though I'd very much hope they
>will retain a copy mode to allow use in partition scenarios.
>
>With that background I think the common denominator between them and
>the main idea behind ISM is that they facilitate communication via
>memory buffers and very simple and reliable copy/share operations. I
>think this would also capture our planned use-case of devices (TTYs,
>block devices, framebuffers + HID etc) provided by a peer on top of
>such a memory communication device.

Make sense, I agree with MCD.

Best regard,
Dust