Re: mmaping on plan9? (was Re: [9fans] venti /plan9port mmapped

["hiro via 9fans" <9fans@9fans.net>]

[-- Attachment #1: Type: text/plain, Size: 2054 bytes --]

you're saying you want the software to be more simple, but at the same time
you say you want to exploit some techniques that make the hardware use more
efficient.

the first goal is commendable, but for the second you have to first
understand how the hardware actually works. i suggest you share the insight
that makes you believe mmap is "more efficient" than reading a large file.

i see a lot of talk about mapping executables. in our special case on plan9
the executables are so small they might fit in L1 cache.
The whole 9front distribution with all documentation and git history fits
in L3 cache of modern cpus.

Maybe just change iosize and be done?

On Thu, Feb 12, 2026 at 6:44 AM Alyssa M via 9fans <9fans@9fans.net> wrote:

> Ah oops - I forgot to repeat my mention of copy-on-write from my first
> post:
>
> On Thursday, February 05, 2026, at 9:30 PM, Alyssa M wrote:
>
> I tend to think about mmap the same way I do about vfork: with the right
> virtual memory system and file system it shouldn't be necessary. A
> combination of demand paging* and copy-on-write* should make read/write
> of large areas of files as efficient as memory mapping - the main
> difference being that, with read/write, memory is isolated from both the
> file and other processes, whereas memory mapping  implies some degree of
> sharing. On the whole I think I'd rather have the isolation.
>
>
> Without that it makes no sense! Sorry!
> *9fans <https://9fans.topicbox.com/latest>* / 9fans / see discussions
> <https://9fans.topicbox.com/groups/9fans> + participants
> <https://9fans.topicbox.com/groups/9fans/members> + delivery options
> <https://9fans.topicbox.com/groups/9fans/subscription> Permalink
> <https://9fans.topicbox.com/groups/9fans/Te8d7c6e48b5c075b-M718007f34efa7d6c391d0583>
>

------------------------------------------
9fans: 9fans
Permalink: https://9fans.topicbox.com/groups/9fans/Te8d7c6e48b5c075b-M21196aae4eff578310ffe2b1
Delivery options: https://9fans.topicbox.com/groups/9fans/subscription

[-- Attachment #2: Type: text/html, Size: 2649 bytes --]