Date: Mon, 13 Jan 2003 20:14:07 -0800 From: Peter Wemm <peter@wemm.org> To: "Alan L. Cox" <alc@imimic.com> Cc: Matthew Dillon <dillon@apollo.backplane.com>, arch@FreeBSD.ORG Subject: Re: Virtual memory question Message-ID: <20030114041407.DDFC32A89E@canning.wemm.org> In-Reply-To: <3E2381F8.85BB90A0@imimic.com>
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"Alan L. Cox" wrote:
> Peter Wemm wrote:
> >
> > "Alan L. Cox" wrote:
> > > Matthew Dillon wrote:
> > > > ...
> > > > How about something like:
> > > >
> > > > getmemfd().
> > > >
> > >
> > > Roughly speaking, this is shm_open(3), which we currently implement
> > > using files.
> >
> > .. which is expressly what I wanted to avoid.
> >
>
> Your response is ambiguous. :-) It doesn't say whether you want to
> avoid shm_open(3) the interface or rather FreeBSD's implementation of
> it. Personally, I'm all for changing the implementation in the way Matt
> describes, but I haven't yet heard a rationale for a new interface.
> Specifically, the interface proposed thus far could be emulated by
>
> fd = shm_open("unique name", ...);
> shm_unlink("unique name");
>
> The spec also seems to makes the creation of unique names easy: "If name
> does not begin with the slash character, the effect is
> implementation-dependent." So, a per-process name space is allowed for
> names not beginning with slash.
>
> Furthermore, the only operations that I know of on a "path" are
> shm_open() and shm_unlink(), and my reading of those was that a hash
> table keyed on the "path" was a legal implementation.
>
> In summary, a new implementation would be good, but I haven't seen the
> rationale for a new interface, especially given that shm_open(3) is an
> existing standard.
Sorry about the ambiguity.
My problem with the shm_*() calls is that the API is pretty heavily tied to
the file system. If there is a way to avoid that, then fine. It looks
like one needs to ftruncate() it to resize a shm_open() object.
Cheers,
-Peter
--
Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com
"All of this is for nothing if we don't go to the stars" - JMS/B5
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