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

[ron minnich <rminnich@gmail.com>]

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I still think an external pager interface would be both easier and more
useful than the unix mmap api.

On Mon, Feb 9, 2026 at 11:57 AM Bakul Shah via 9fans <9fans@9fans.net>
wrote:

> Exactly. And the same failure modes exist (if your swap device or exec
> file access suddenly fails). In general Unix-type OSes only handle the
> "happy path" well and do not expend heroic efforts to deal with errors.
>
> Here by mmap  Ron and I mean memory mapping and not linux/BSD specific
> mmap *API*. If any mmap API is added to plan9, it need not follow the
> example of linux/BSD but it should be well integrated.
>
> On Feb 9, 2026, at 7:23 AM, ron minnich <rminnich@gmail.com> wrote:
>
> as for mmap, there's already a defacto mmap happening for executables.
> They are not read into memory. In fact, the first instruction you run in a
> binary results in a page fault.
>
> Consider a binary larger than your physical memory (this can happen).
> Without the defacto mmap, you could not run it.
>
> Similarly, in HPC, there are data sets far larger than physical memory.
> mmap makes use of these data sets manageable. Nothing else has been
> proposed which comes close.
>
> ron
>
> On Sun, Feb 8, 2026 at 5:35 PM ron minnich <rminnich@gmail.com> wrote:
>
>> suns would survive server outages. At least in the 90s. Linux NFS had its
>> own ideas for failure.
>>
>> Statelessness, like everything, has its good and bad points. Note that
>> NFS was never truly stateless for v2 and later; servers had to have a dup
>> cache, for practical reasons.
>>
>> Stateless is not cheap. NFS does not even have a mount rpc, for example,
>> so every packet carries with it authentication information and user
>> identity. Every. Single. One.
>>
>> But you could reboot a server, and you'd see the infamous "nfs server not
>> responding still trying" on the client for hard mounts. For soft mounts,
>> you'd see data loss. For spongy mounts, well, some combination of the two
>> :-)
>>
>> When all is said and done, like it or not, NFS has had greater success
>> than 9p, for all kinds of reasons, some of which make sense, others which
>> don't.
>>
>>
>>
>> On Sun, Feb 8, 2026 at 1:01 PM Ethan Azariah <eekee57@fastmail.fm> wrote:
>>
>>> On Sun, Feb 8, 2026, at 3:10 PM, Alyssa M wrote:
>>> > I seem to recall NFS will even
>>> > survive a server reboot by being stateless (not that I've actually
>>> > tried that...)
>>> 
>>> I forget exactly which NFS version I was using back in 2004, but
>>> programs with open files didn't survive me tripping over an ethernet cable
>>> despite the disconnect not lasting 10 seconds. Server & client were Linux.
>>> I remember wondering what NFS's statelessness was for, exactly, though I
>>> guess the failure to 'come back' might have been an implementation issue.
>>> Newer NFS versions aren't stateless.
>>> 
>>> Surviving a server reboot would be nice though. :)
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