Re: [uml-devel] When /tmp is not tmpfs.

[Rob Landley <rob@landley.net>]

On Tuesday 29 November 2005 10:08, Blaisorblade wrote:
> On Monday 28 November 2005 02:07, Rob Landley wrote:
> > On Sunday 27 November 2005 12:31, Nix wrote:
> >
> > Did you catch Linus's long rant about how MAP_PRIVATE is deeply stupid
> > and that Linux will never really implement it?
>
> What's that?

Looking it up, it turns out it was MAP_COPY he was against:
http://www.uwsg.iu.edu/hypermail/linux/kernel/0110.0/0826.html

So I was wrong there.

> > And you can fsync and do stuff like journaling within a file.  (Except
> > with mmap it's msync.)
> >
> > No, just use the madvise(NO_SYNC).
>
> Which doesn't exist.

Takes some of the fun out of it, yes.  But as a recommendation in response to 
a similar "change everything" proposal, it seems like a more sane direction 
to me.

> > Then tmpfs becomes completely
> > irrelevant because any arbitrary file backed mapping can be treated as
> > memory.  (Not pinned, but still treated as shared memory.)
> >
> > I vaguely remember some discussion about this on linux-kernel, some time
> > ago. I wonder how it came out?  (2.6.15-rc2 mman.h doesn't show
> > anything...)
>
> What I remember is MADV_TRUNCATE / MADV_FREE / and so on by Badary
> Pulavarty - the equivalent of MADV_DONTNEED with additional truncation of
> the tmpfs pages you have mmaped.
>
> Which is used for UML memory hotunplug patch from Jeff's. IIRC it's in -mm,
> but won't be in 2.6.15 at this point.

This is a vague recollection from 3-5 years ago. :)

Rob
-- 
Steve Ballmer: Innovation!  Inigo Montoya: You keep using that word.
I do not think it means what you think it means.


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