linux-kernel - Re: [QUESTION] about the maple tree and current status of mmap

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Date:   Thu, 29 Dec 2022 17:10:28 +0000
From:   Lorenzo Stoakes <lstoakes@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Hyeonggon Yoo <42.hyeyoo@...il.com>, linux-mm@...ck.org,
        liam.howlett@...cle.com, surenb@...gle.com, ldufour@...ux.ibm.com,
        michel@...pinasse.org, vbabka@...e.cz, linux-kernel@...r.kernel.org
Subject: Re: [QUESTION] about the maple tree and current status of mmap_lock
 scalability

On Thu, Dec 29, 2022 at 04:51:37PM +0000, Matthew Wilcox wrote:
> The mmap_lock is taken for many, many things.  [snip]

I am currently describing the use of this lock (for 6.0) in the book and it is
striking just how broadly it's used. I'm diagramming it out for 'core' users,
i.e. non-driver and non-some other things, but even constraining that leaves a
HUGE number of users. I've also documented the 'unexpected' uses of the
page_table_lock, which seems to have been significantly improved over time but
still a few cases remain!

Am happy to give you (+ anybody else on MAINTAINERS list) an early copy of the
relevant bit (once I've finished the diagrams anyway) if that'd be helpful!

Now if you guys could stop obsoleting my work that'd be great ;)