Linux-kernel mailing list archive 1998-10,: Re: mmap() versus read()

# Re: mmap() versus read()

Benjamin C.R. LaHaise (blah@kvack.org)
Wed, 11 Mar 1998 12:37:35 -0500 (EST)

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On Wed, 11 Mar 1998, Michael Lausch wrote:
....
> But the problem is when you are using Linux on embedded systems
> without any swap (disk) at all. The programs are stored in the FLASH
> RAM so the cost of reading a page from the executable is almost zero,
> but using a swap area is impossible (no, we don't have 20 Meg RAM for
> a RAM swap disk)

Is this paged flash or memory mapped flash? Ideally an embedded system
would use memory-mapped flash with a filesystem like romfs (? - does it do
this?) that would provide it's own mmap that just maps in the page, still
in flash, into the process on nopage. This way your executables take up
practically no ram under normal circumstances.

Something I didn't mention about the swap-caching of executables and such:
it would only be enabled via a mount option, or the traditional sticky
bit, so it shouldn't impact embedded systems.

-ben

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