The whole DISCARDABLE thing was a relic of pre-NT versions of Windows, back when people were just beginning to realize that 640K was not, in fact, enough for everybody. I'm surprised the kernel pays any attention to it at all anymore. There's not much upside to paging memory associated with drivers in and out. Certainly not worth the additional attack surface that you get by making things more complicated than necessary.
Pre-NT? Are you sure? My understanding of history is that the PE file format was part of NT 3. I would have thought that earlier systems kept as much paged as possible, but maybe that's wrong.
Maybe it's not worth it any more. My phone has 8GB of memory. I do remember a time when you could boot Windows XP on a system with 64MB of RAM when you needed special configuration / custom kernels to boot Linux on such a system. You would think that this was because of the pile of small choices made to relieve memory pressure...
> I do remember a time when you could boot Windows XP on a system with 64MB of RAM when you needed special configuration / custom kernels to boot Linux on such a system.
No, you're misremembering. A Linux kernel has never needed anywhere near that much RAM to boot. The first machine I used Linux on had 8MB RAM and that was considered plenty at the time. I do remember KDE being pretty slow on a machine with 64MB...maybe you're thinking of desktop environments.
My first X86 machine running Linux was a 386DX/33 with 4MB of RAM. It booted the Linux 0.96 kernel (IIRC) just fine and I also used X on that machine. As far as I remember, I did have 16MB swap as well to make things actually usable, but the kernel itself would boot just fine with just the 4MB RAM.
If memory serves me right, it was actually possible to get the kernel to boot with as little as 2MB in those days, but that was the limit.
I remember a custom kernel compile on this machine took a little over 24 hours. :-/
Yes, but the point is that movable/discardable flags are an old-school hack that probably shouldn't have made it into modern binary file formats to begin with.
