From: Gregory Price <gourry@gourry.net>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: John Groves <john@jagalactic.com>, John Groves <John@groves.net>,
Miklos Szeredi <miklos@szeredi.hu>,
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Subject: Re: [PATCH v13 10/12] famfs: Add runtime operation-permission (opts) framework
Date: Sun, 23 Aug 2026 12:43:14 -0400 [thread overview]
Message-ID: <aosejKmNJxCIpQho@gourry-fedora-PF4VCD3F> (raw)
In-Reply-To: <20260822174029.GC6110@frogsfrogsfrogs>
On Sat, Aug 22, 2026 at 10:40:29AM -0700, Darrick J. Wong wrote:
>
> A bigger question I just thought of is sharing cxlmem between files (aka
> reflink). Is that allowed? I could see a theoretical usecase for
> programs A and B wanting to share some cxlmem for communication or
> heartbeats whilst having their own /a and /b files for their private
> memory. Probably you'd just create a /common file to do that and not
> map the same cxlmem page into /a and /b, right?
>
If the underlying memory hardware is hardware-coherent, then this would
be supportable because the coherence domains of all the hosts connected
to the large pool would extend to one another.
In our current world, these huge-memory distributed memory systems are
non-coherent and each host's coherence domain stops more or less at the
head it uses to connect to the shared media (it's probably more accurate
to say it's "device dependant" but that's besides the point).
Anyway, there's "allowed" and "useful". You could technically do it
(maybe not with FAMFS' current guard rails) - but it would be useless
unless Process A and Process B were in the same coherence domain.
~Gregory
next prev parent reply other threads:[~2026-08-23 16:43 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20260810202325.96202-1-john@jagalactic.com>
2026-08-10 20:23 ` [PATCH v13 00/12] famfs: the Fabric-Attached Memory File System (standalone) John Groves
2026-08-10 20:24 ` [PATCH v13 01/12] dax: replace exported dax_dev_get() with non-allocating dax_dev_find() John Groves
2026-08-10 20:24 ` [PATCH v13 02/12] famfs: Module operations, fs_context, and mount John Groves
2026-08-10 20:24 ` [PATCH v13 03/12] famfs: Add daxdev table and dax notify_failure support John Groves
2026-08-10 20:24 ` [PATCH v13 04/12] famfs: Introduce inode_operations and super_operations John Groves
2026-08-10 20:24 ` [PATCH v13 05/12] famfs: Introduce file_operations read/write John Groves
2026-08-10 20:25 ` [PATCH v13 06/12] famfs: Introduce mmap and VM fault handling John Groves
2026-08-10 20:25 ` [PATCH v13 07/12] famfs: MAP_CREATE ioctl and fmap ingest (ABI 44) John Groves
2026-08-11 8:03 ` Richard Cheng
2026-08-11 22:17 ` John Groves
[not found] ` <20260822001723.GC6047@frogsfrogsfrogs>
2026-08-22 19:23 ` John Groves
2026-08-10 20:25 ` [PATCH v13 08/12] famfs: iomap_begin and file-to-dax offset resolution John Groves
2026-08-10 20:25 ` [PATCH v13 09/12] famfs: Register secondary daxdevs by path (FAMFSIOC_DAXDEV_OPEN) John Groves
2026-08-10 20:25 ` [PATCH v13 10/12] famfs: Add runtime operation-permission (opts) framework John Groves
2026-08-22 0:07 ` Darrick J. Wong
2026-08-22 4:18 ` Gregory Price
2026-08-22 17:40 ` Darrick J. Wong
2026-08-22 21:57 ` John Groves
2026-08-23 16:43 ` Gregory Price [this message]
2026-08-23 16:57 ` Gregory Price
2026-08-10 20:25 ` [PATCH v13 11/12] famfs: Report device capacity via statfs so df works John Groves
2026-08-10 20:26 ` [PATCH v13 12/12] famfs: Add documentation John Groves
2026-08-20 12:37 ` [PATCH v13 00/12] famfs: the Fabric-Attached Memory File System (standalone) Jeff Layton
2026-08-22 0:19 ` Darrick J. Wong
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