On 6/12/19 10:00 AM, Dave Hansen wrote: > On 6/12/19 6:32 AM, Lendacky, Thomas wrote: >> Create a section for SME in the vmlinux.lds.S. Position it after "_end" >> so that the memory will be reclaimed during boot and, since it is all >> zeroes, it compresses well. > > I don't think I realized that things after _end get reclaimed. Do we do > that at the same spot that we do init data or somewhere else?
I was looking at the start of setup_arch() in arch/x86/kernel/setup.c, where there's a memblock_reserve() done for the kernel (it reserves from _text to __bss_stop, not all the way to _end, and later the brk area is reserved). At that point, my take was that the memory outside the reserved area is now available (and there's a comment below that to that effect, also), so the .sme section would basically be discarded and re-claimed for general page usage. > > How much does compressing 8MB of zeros slow down my kernel compile? ;) Heh, I didn't measure that. :) Thanks, Tom >
