Re: [9fans] venti /plan9port mmapped

[Ron Minnich <rminnich@p9f.org>]

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


ron

On Fri, Jan 2, 2026 at 1:02 PM Bakul Shah via 9fans <9fans@9fans.net> wrote:
>
> Might be an opportunity for optimizing mmap + virtual memory architecture for database specific applications.... (should be worth at least a few papers for the academic crowd).
>
> > On Jan 2, 2026, at 12:39 PM, ori@eigenstate.org wrote:
> >
> > You may want to read this: https://db.cs.cmu.edu/mmap-cidr2022/
> >
> > Quoth wb.kloke@gmail.com:
> >> Further trying to sanitize venti, I decided to change my mventi (no isects) for mmap IO.
> >>
> >> At a first stage I mmap the whole venti i arena partition (current size 80GB, filled to 44GB). On a 64bit processor this is not a big thing, and replace the file operations (rwpart in part.c  and readarena in arena.c) by memmove.
> >>
> >> As it works on amd64 FreeBSD, I can now eliminate the block cache  and its complications (IO over block boundaries) from the source making the remaining source much clearer.
> >>
> >> The price is, that I have to rely on demand paging of the OS. So it is probably not easily portable to plan9 or 9front.
> >>
> >> Can any body give ime a hint, how to map a partition to a segment in 9front?

------------------------------------------
9fans: 9fans
Permalink: https://9fans.topicbox.com/groups/9fans/Tf991997f4e7bb37e-M44817a56f8c46bcdac466b1b
Delivery options: https://9fans.topicbox.com/groups/9fans/subscription