From: Waldemar Kozaczuk <jwkozac...@gmail.com>
Committer: Nadav Har'El <n...@scylladb.com>
Branch: master
Start using memory below kernel
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
Signed-off-by: Waldemar Kozaczuk <jwkozac...@gmail.com>
Message-Id: <20190605043342.31586-1-jwkozac...@gmail.com>
---
diff --git a/arch/x64/arch-setup.cc b/arch/x64/arch-setup.cc
--- 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);
--
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