ProcessManager: Show some basic system memory stats below the process table.

This really improves the feeling of "system overview" :^)

Applications/ProcessManager/MemoryStatsWidget.cpp

@@ -0,0 +1,101 @@
+#include "MemoryStatsWidget.h"
+#include <SharedGraphics/Painter.h>
+#include <LibGUI/GBoxLayout.h>
+#include <LibGUI/GLabel.h>
+#include <LibGUI/GStyle.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+MemoryStatsWidget::MemoryStatsWidget(GWidget* parent)
+    : GWidget(parent)
+{
+    set_size_policy(SizePolicy::Fill, SizePolicy::Fixed);
+    set_preferred_size({ 0, 60 });
+
+    set_layout(make<GBoxLayout>(Orientation::Vertical));
+    layout()->set_margins({ 0, 8, 0, 0 });
+    layout()->set_spacing(3);
+
+    m_user_physical_pages_label = new GLabel(this);
+    m_user_physical_pages_label->set_size_policy(SizePolicy::Fill, SizePolicy::Fixed);
+    m_user_physical_pages_label->set_preferred_size({ 0, 12 });
+    m_user_physical_pages_label->set_fill_with_background_color(false);
+    m_supervisor_physical_pages_label = new GLabel(this);
+    m_supervisor_physical_pages_label->set_fill_with_background_color(false);
+    m_supervisor_physical_pages_label->set_size_policy(SizePolicy::Fill, SizePolicy::Fixed);
+    m_supervisor_physical_pages_label->set_preferred_size({ 0, 12 });
+    m_kmalloc_label = new GLabel(this);
+    m_kmalloc_label->set_fill_with_background_color(false);
+    m_kmalloc_label->set_size_policy(SizePolicy::Fill, SizePolicy::Fixed);
+    m_kmalloc_label->set_preferred_size({ 0, 12 });
+
+    start_timer(1000);
+    refresh();
+}
+
+MemoryStatsWidget::~MemoryStatsWidget()
+{
+}
+
+static inline size_t page_count_to_kb(size_t kb)
+{
+    return (kb * 4096) / 1024;
+}
+
+static inline size_t bytes_to_kb(size_t bytes)
+{
+    return bytes / 1024;
+}
+
+void MemoryStatsWidget::refresh()
+{
+    FILE* fp = fopen("/proc/memstat", "r");
+    if (!fp) {
+        perror("failed to open /proc/memstat");
+        exit(1);
+    }
+
+    for (;;) {
+        char buf[BUFSIZ];
+        char* ptr = fgets(buf, sizeof(buf), fp);
+        if (!ptr)
+            break;
+        auto parts = String(buf, Chomp).split(',');
+        if (parts.size() < 7)
+            break;
+        bool ok;
+        unsigned kmalloc_sum_eternal = parts[0].to_uint(ok);
+        ASSERT(ok);
+        unsigned kmalloc_sum_alloc = parts[1].to_uint(ok);
+        ASSERT(ok);
+        unsigned kmalloc_sum_free = parts[2].to_uint(ok);
+        ASSERT(ok);
+        unsigned user_pages_alloc = parts[3].to_uint(ok);
+        ASSERT(ok);
+        unsigned user_pages_free = parts[4].to_uint(ok);
+        ASSERT(ok);
+        unsigned supervisor_pages_alloc = parts[5].to_uint(ok);
+        ASSERT(ok);
+        unsigned supervisor_pages_free = parts[6].to_uint(ok);
+        ASSERT(ok);
+
+        m_kmalloc_label->set_text(String::format("Kernel heap: %uK allocated, %uK free\n", bytes_to_kb(kmalloc_sum_alloc), bytes_to_kb(kmalloc_sum_free)));
+        m_user_physical_pages_label->set_text(String::format("Userspace physical: %uK allocated, %uK free\n", page_count_to_kb(user_pages_alloc), page_count_to_kb(user_pages_free)));
+        m_supervisor_physical_pages_label->set_text(String::format("Supervisor physical: %uK allocated, %uK free\n", page_count_to_kb(supervisor_pages_alloc), page_count_to_kb(supervisor_pages_free)));
+        break;
+    }
+
+    fclose(fp);
+}
+
+void MemoryStatsWidget::timer_event(GTimerEvent&)
+{
+    refresh();
+}
+
+void MemoryStatsWidget::paint_event(GPaintEvent& event)
+{
+    Painter painter(*this);
+    painter.set_clip_rect(event.rect());
+    GStyle::the().paint_surface(painter, rect());
+}