memory: count up total physical memory

arch/x64/arch-setup.cc

@@ -49,6 +49,7 @@ void arch_setup_free_memory()
     while (p < tmp + mb.mmap_length) {
         auto ent = static_cast<e820ent*>(p);
         if (ent->type == 1) {
+            memory::phys_mem_size += ent->size;
             if (ent->addr < edata) {
                 u64 adjust = std::min(edata - ent->addr, ent->size);
                 ent->addr += adjust;

mempool.cc

@@ -8,6 +8,8 @@
 
 namespace memory {
 
+size_t phys_mem_size;
+
 // Memory allocation strategy
 //
 // The chief requirement is to be able to deduce the object size.

mempool.hh

@@ -11,6 +11,8 @@ using std::size_t;
 
 const size_t page_size = 4096;
 
+extern size_t phys_mem_size;
+
 void* alloc_page();
 void free_page(void* page);
 void* alloc_page_range(size_t bytes);