Messages in this thread | | | Date | Mon, 22 Mar 2004 18:52:04 -0600 | From | Matt Mackall <> | Subject | Re: [PATCH] 2.6: mmap complement, fdmap |
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On Mon, Mar 22, 2004 at 01:26:01PM -0600, Matt Miller wrote: > > > > a) what the hell for? > > > > > > It's targetted mainly as a performance enhancer. Some of the specific > > > scenarios where it would be useful are: > > > > > > a) When one cannot afford to take the performance hit of synchronizing > > > a memory range to disk due to disk size limitations or speed > > > requirements. > > > b) Some things can benefit from the ability to interface with > > memory as a > > > file. > > > > > > The specific reason for implementing this was to allow for > > loading dynamic > > > libraries in the context of a process without having to write them to > > > disk. > > > > How about tmpfs/ramfs instead? Open a file on tmpfs and mmap it and > > you've got the same thing without any of the nasty corner cases. > > Because tmpfs does not allow you to map a file descriptor to a specific > memory > range inside a process. tmpfs allows you to open a file that exists only > in memory, yes, but it does not accomplish what fdmap tries to accomplish. > fdmap allows you to access arbitrary memory ranges as if they were a file. > tmpfs allows you to access a file that happens to only exist in memory. > You do not control the address range that tmpfs/ramfs map to.
You don't? Is this not what the first argument of mmap provides? I'm afraid I can't see how it matters, as you'd have to populate said map afterwards anyway.
Point is, mmap() is already its own complement and what you're proposing is a hairy solution in search of a problem as the VFS maintainer already pointed out.
-- Matt Mackall : http://www.selenic.com : Linux development and consulting - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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