From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Matthew Wilcox <willy@infradead.org>
Cc: lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org,
linux-fsdevel@vger.kernel.org
Subject: Re: [LSF/MM/BPF] Whither Highmem?
Date: Mon, 8 May 2023 02:43:30 +0300 [thread overview]
Message-ID: <20230507234330.cnzbumof2hdl4ci6@box.shutemov.name> (raw)
In-Reply-To: <ZFgySub+z210Rvsk@casper.infradead.org>
On Mon, May 08, 2023 at 12:20:42AM +0100, Matthew Wilcox wrote:
>
> I see there's a couple of spots on the schedule open, so here's something
> fun we could talk about.
>
> Highmem was originally introduced to support PAE36 (up to 64GB) on x86
> in the late 90s. It's since been used to support a similar extension
> on ARM (maybe other 32-bit architectures?)
>
> Things have changed a bit since then. There aren't a lot of systems
> left which have more than 4GB of memory _and_ are incapable of running a
> 64-bit kernel.
Actual limit is lower. With 3G/1G userspace/kernel split you will have
somewhere about 700Mb of virtual address space for direct mapping.
But, I would like to get rid of highmem too. Not sure how realistic it is.
--
Kiryl Shutsemau / Kirill A. Shutemov
next prev parent reply other threads:[~2023-05-07 23:43 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-07 23:20 Matthew Wilcox
2023-05-07 23:43 ` Kirill A. Shutemov [this message]
2023-05-08 0:23 ` Matthew Wilcox
2023-05-08 0:59 ` Kirill A. Shutemov
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