linux-kernel - Re: [PATCH v2 0/6] kernfs: proposed locking and concurrency improvement

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Date:   Tue, 23 Jun 2020 19:13:48 -0400
From:   Tejun Heo <tj@...nel.org>
To:     Rick Lindsley <ricklind@...ux.vnet.ibm.com>
Cc:     Ian Kent <raven@...maw.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        David Howells <dhowells@...hat.com>,
        Miklos Szeredi <miklos@...redi.hu>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/6] kernfs: proposed locking and concurrency
 improvement

Hello, Rick.

On Mon, Jun 22, 2020 at 02:22:34PM -0700, Rick Lindsley wrote:
> > I don't know. The above highlights the absurdity of the approach itself to
> > me. You seem to be aware of it too in writing: 250,000 "devices".
> 
> Just because it is absurd doesn't mean it wasn't built that way :)
> 
> I agree, and I'm trying to influence the next hardware design. However,

I'm not saying that the hardware should not segment things into however many
pieces that it wants / needs to. That part is fine.

> what's already out there is memory units that must be accessed in 256MB
> blocks. If you want to remove/add a GB, that's really 4 blocks of memory
> you're manipulating, to the hardware. Those blocks have to be registered
> and recognized by the kernel for that to work.

The problem is fitting that into an interface which wholly doesn't fit that
particular requirement. It's not that difficult to imagine different ways to
represent however many memory slots, right? It'd take work to make sure that
integrates well with whatever tooling or use cases but once done this
particular problem will be resolved permanently and the whole thing will
look a lot less silly. Wouldn't that be better?

Thanks.

-- 
tejun