Re: [9fans] venti /plan9port mmapped

[Shawn Rutledge <lists@ecloud.org>]

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> On Jan 6, 2026, at 23:59, Ron Minnich <rminnich@p9f.org> wrote:
> 
> back in the NIX days, when we had 32GiB of memory mapped with 32 1-G
> PTEs, I wrote a trivial venti that ONLY used dram. That was easy.
> Because you can keep up a single machine with 32G up for an
> arbitrarily long time, I did not bother with a disk. This work was
> based on the fact that lsub had used very little of their 32G coraid
> server (something like 3G? I forget) over ten years: venti dedups by
> its nature and that's your friend.
> 
> So maybe a pure-ram venti, with a TiB or so of memory, could work?
> 
> "disks are the work of the devil" — jmk

I’ve been wondering why it’s still so rare to map persistent storage to memory addresses, in hardware.  It seemed like Intel Optane was going to go there, for a while, then they just gave up on the idea.  And core memory was already persistent, back in the day.

I think universal memory should happen eventually; and to prepare for that, software design should go towards organizing data the same in memory as on storage: better packing rather than lots of randomness in the heap, and memory-aligned structures. Local file I/O might become mostly unnecessary, but could continue as an abstraction to organize things in memory, at the cost of having to keep writing I/O code.  So if that’s where we are going, mmap is a good thing to have.  But yeah, maybe it’s more hassle as an abstraction for network-attached storage.

Wasn’t this sort of thing being done in the PDA era?  I never developed for the Newton, but I think a “soup” is such a persistent structure.  And maybe whatever smalltalk does with their sandboxes.  Is it just a persistent heap or is it organized better?


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