From: Matthew Wilcox <willy@infradead.org>
To: Oscar Salvador <osalvador@suse.de>
Cc: lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org
Subject: Re: [LSF/MM/BFP TOPIC] Deprecate SPARSEMEM and have only SPARSEMEM_VMEMMAP
Date: Fri, 10 May 2024 23:03:58 +0100 [thread overview]
Message-ID: <Zj6ZzmpBr3BgLeaA@casper.infradead.org> (raw)
In-Reply-To: <Zj3i0pCJd3ETxQNU@localhost.localdomain>
On Fri, May 10, 2024 at 11:03:14AM +0200, Oscar Salvador wrote:
> I did some research on which arches use CONFIG_SPARSE_MEMMAP/VMEMMAP or
> none(using flatmem?).
>
> SPARSE_MEMMAP SPARSE_VMEMMAP
> arc
> arm X
> arm64 X X
> csky
> hexagon
> loongarch X X
> m68k
> microblaze
> mips X
> nios2
> openrisc
> parisc
> powerpc X X
> riscv X X
> s390 X X
> sh X
> sparc X X
> um
> x86 X X
> xtensa
>
> arm, mips, parisc and sh operate with SPARSE_MEMMAP but are lacking code for
> SPARSE_VMEMMAP.
> I think these archs should be the first thing to focus on, to see if we can
> make them work on SPARSE_VMEMMAP.
> If we can, and when all arches can run on SPARSE_VMEMMAP, we can think of killing
> SPARSE_MEMMAP.
I'm a little concerned about having this conversation without the
affected architecture maintainers in the room. However, I can speak to
PA-RISC.
Early models have a dense memory layout and we need not be concerned
with them. I'm not quite sure about the PA-7200 to PA-8500 ccio based
machines, would need to do some research. For the PA-8500+ astro based
machines, the 256MB that would be in the range 3.75GB to 4GB is
relocated to 67.75-68GB to leave space for PCI mmio. So if you have
a machine with 8GB of memory (fairly typical for a J6000 machine),
you'd have three ranges of memory:
0-3.75GB
4-8GB
67.75-68GB
and I'd like to see an analysis of how laying out memmap would differ
for those machines.
The PA-8800+ pluto chipset does something similar, except it
supports more memory and more PCI mmio, so a 32GB rp3440 would have
a memmap:
0-3GB
4-32GB
259-260GB
I think this would actually work better as three zones rather than
three sections. It might match quite well with the TAO proposal.
next prev parent reply other threads:[~2024-05-10 22:04 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-10 9:03 [LSF/MM/BFP TOPIC] Deprecate SPARSEMEM and have only SPARSEMEM_VMEMMAP Oscar Salvador
2024-05-10 22:03 ` Matthew Wilcox [this message]
2024-05-13 9:43 ` Oscar Salvador
2024-05-13 10:12 ` Oscar Salvador
2024-05-13 23:02 ` Mike Rapoport
2024-05-12 13:45 ` Mike Rapoport
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Zj6ZzmpBr3BgLeaA@casper.infradead.org \
--to=willy@infradead.org \
--cc=linux-mm@kvack.org \
--cc=lsf-pc@lists.linux-foundation.org \
--cc=osalvador@suse.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).