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Date: Sun, 17 Dec 2023 15:40:19 +0000
From: Matthew Wilcox <willy@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Yu Zhao <yuzhao@google.com>, Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Jesse Barnes <jsbarnes@google.com>,
	Suren Baghdasaryan <surenb@google.com>,
	Guru Anbalagane <gurua@google.com>,
	David Rientjes <rientjes@google.com>
Subject: Re: [GIT PULL] hotfixes for 6.7-rc6
Message-ID: <ZX8WY7s76KYr3jRE@casper.infradead.org>
References: <20231215071604.946a433bbc05a6409faf5a33@linux-foundation.org>
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On Sat, Dec 16, 2023 at 04:16:45PM -0800, Linus Torvalds wrote:
> On Fri, 15 Dec 2023 at 20:57, Yu Zhao <yuzhao@google.com> wrote:
> >
> > There has been a short-term plan, i.e., moving some of folio->flags to
> > the lower bits of folio->lru so that we can drop the Kconfig
> > constraint. I have discussed this with Willy but never acted on it. My
> > priority has been to surface more of our ideas that can potentially
> > save users money on memory to the community. I'm CC'ing our team
> > leads. Please feel free to let us know your preference on the
> > priority.
> 
> This is definitely a "eventually" thing on my wishlist, so I was more
> just wanting to hear that there is a plan, and somebody working on
> it..

"eventually" we should get rid of LRUs altogether.  They're no good for
a modern CPU.

https://lore.kernel.org/linux-mm/ZTc7SHQ4RbPkD3eZ@casper.infradead.org/

I don't have much more in the way of thoughts on what this might look
like beyond that email.  I'm inclined towards something incredibly simple
like taking each 4MB chunk of memory in turn; freeing inactive pages
and marking active pages as inactive.