On Wed, Jun 5, 2019 at 7:33 AM Waldemar Kozaczuk <jwkozac...@gmail.com>
wrote:
> This patch improves memory utilization by
> making OSv use area below where kernel is loaded.
>
> This normally saves only 1M + 640K (low memory)
> howewer makes bigger difference when kernel_base in
> Makefile is bumped higher. So if one changes kernel_base
> to 10M then before this patch we would waste almost 10M of
> memory.
>
> Fixes #1012
>
Thanks. I committed this, and tested that it actually allows me to run my
favorite application (rogue ;-))
with 1MB less.
I'm curious if there isn't a problem with the physical address "0". Is it
ok that we go all the way to 0, or
does this code only starts somewhere else (I don't remember any details
about this code... sorry...).
> Signed-off-by: Waldemar Kozaczuk <jwkozac...@gmail.com>
> ---
> arch/x64/arch-setup.cc | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x64/arch-setup.cc b/arch/x64/arch-setup.cc
> index 9317dd25..62236486 100644
> --- a/arch/x64/arch-setup.cc
> +++ b/arch/x64/arch-setup.cc
> @@ -130,7 +130,7 @@ void arch_setup_free_memory()
> // freed.
> for_each_e820_entry(e820_buffer, e820_size, [] (e820ent ent) {
> // can't free anything below edata, it's core code.
> - // FIXME: can free below 2MB.
> + // can't free anything below kernel at this moment
> if (ent.addr + ent.size <= edata) {
> return;
> }
> @@ -159,6 +159,16 @@ void arch_setup_free_memory()
> // now that we have some free memory, we can start mapping the rest
> mmu::switch_to_runtime_page_tables();
> for_each_e820_entry(e820_buffer, e820_size, [] (e820ent ent) {
> + //
> + // Free the memory below elf_start which we could not before
> + if (ent.addr < (u64)elf_start) {
> + if (ent.addr + ent.size >= (u64)elf_start) {
> + ent = truncate_above(ent, (u64) elf_start);
> + }
> + mmu::free_initial_memory_range(ent.addr, ent.size);
> + return;
> + }
> + //
> // Ignore memory already freed above
> if (ent.addr + ent.size <= initial_map) {
> return;
> @@ -167,7 +177,7 @@ void arch_setup_free_memory()
> ent = truncate_below(ent, initial_map);
> }
> for (auto&& area : mmu::identity_mapped_areas) {
> - auto base = reinterpret_cast<void*>(get_mem_area_base(area));
> + auto base = reinterpret_cast<void*>(get_mem_area_base(area));
> mmu::linear_map(base + ent.addr, ent.addr, ent.size, ~0);
> }
> mmu::free_initial_memory_range(ent.addr, ent.size);
> --
> 2.20.1
>
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