Add RAM and VRAM footprint

src/main.zig

@@ -47,6 +47,7 @@ fn kmain(boot_info: *const BootInfo) noreturn {
     con.print("  pitch      : {d} bytes\n", .{fb.pitch});
     con.print("  format     : {s}\n", .{@tagName(fb.format)});
     con.print("  framebuffer: 0x{x:0>16}\n", .{fb.base});
+    con.print ("  footprint  : {d} MiB\n", .{(fb.pitch * fb.height) / (1024 * 1024)});
 
     // Summarise the physical memory the loader handed us. The array is danos's
     // own MemoryRegion, so this is a plain slice — no firmware layout in sight.
@@ -73,9 +74,9 @@ fn kmain(boot_info: *const BootInfo) noreturn {
     // Bring up the physical frame allocator over that map, and prove it works:
     // allocate three frames, then hand them back.
     pmm.init(boot_info.memory_map);
-    const s = pmm.stats();
+    const s1 = pmm.stats();
     con.print("\ndanos: frame allocator online\n", .{});
-    con.print("  free frames: {d} ({d} MiB)\n", .{ s.free_frames, mib(s.free_frames) });
+    con.print("  free frames: {d} ({d} MiB)\n", .{ s1.free_frames, mib(s1.free_frames) });
     const f0 = pmm.alloc();
     const f1 = pmm.alloc();
     const f2 = pmm.alloc();
@@ -94,10 +95,13 @@ fn kmain(boot_info: *const BootInfo) noreturn {
     // Bring up the kernel heap (dynamic allocation), built on the VMM.
     heap.init();
     con.write("\ndanos: kernel heap online\n");
+    // Measure the amount of resources the kernel is actually using
+    const s2 = pmm.stats();
+    con.print("  Kernel Footprint: {d} KiB\n", .{kib(s1.free_frames - s2.free_frames)});
 
     // Register the current context as the first task before enabling preemption.
     sched.init(4);
-    con.write("danos: scheduler online\n");
+    con.write("\ndanos: scheduler online\n");
 
     // Start the timer and unmask interrupts — the kernel now has a heartbeat, and
     // the timer preempts among tasks.
@@ -122,6 +126,10 @@ fn mib(pages: u64) u64 {
     return pages * danos.page_size / (1024 * 1024);
 }
 
+fn kib(frames: u64) u64 {
+    return frames * danos.page_size / (1024);
+}
+
 /// Report a CPU exception in red and halt. There's no fault recovery yet, so any
 /// exception is terminal — but now it prints what and where instead of silently
 /// resetting the machine.