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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Tue, 11 Feb 2020 17:03:02 -0800
Message-ID: <CAHk-=wg1ZDADD3Vuw_sXhmBOrQ2xsp8YWxmtWiA6vG0RT-ZQ+A@mail.gmail.com>
Subject: Re: [PATCH] vfs: keep inodes with page cache off the inode shrinker LRU
To:     Andrew Morton <akpm@linux-foundation.org>,
        Russell King <linux@armlinux.org.uk>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Catalin Marinas <catalin.marinas@arm.com>
Cc:     Johannes Weiner <hannes@cmpxchg.org>,
        Rik van Riel <riel@surriel.com>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Dave Chinner <david@fromorbit.com>,
        Yafang Shao <laoar.shao@gmail.com>,
        Michal Hocko <mhocko@suse.com>, Roman Gushchin <guro@fb.com>,
        Al Viro <viro@zeniv.linux.org.uk>, kernel-team@fb.com
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On Tue, Feb 11, 2020 at 4:47 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> What's the situation with highmem on ARM?

Afaik it's exactly the same as highmem on x86 - only 32-bit ARM ever
needed it, and I was ranting at some people for repeating all the
mistakes Intel did.

But arm64 doesn't need it, and while 32-bit arm is obviosuly still
selling, I think that in many ways the switch-over to 64-bit has been
quicker on ARM than it was on x86. Partly because it happened later
(so all the 64-bit teething pains were dealt with), but largely
because everybody ended up actively discouraging 32-bit on the Android
side.

There were a couple of unfortunate early 32-bit arm server attempts,
but they were - predictably - complete garbage and nobody bought them.
They don't exist any more.

So at least my gut feel is that the arm people don't have any big
reason to push for maintaining HIGHMEM support either.

But I'm adding a couple of arm people and the arm list just in case
they have some input.

[ Obvious background for newly added people: we're talking about
making CONFIG_HIGHMEM a deprecated feature and saying that if you want
to run with lots of memory on a 32-bit kernel, you're doing legacy
stuff and can use a legacy kernel ]

              Linus