From 5a1a76f94e266820de6fbdab06883738ced12f14 Mon Sep 17 00:00:00 2001
From: Daniel Micay <danielmicay@gmail.com>
Date: Thu, 23 Aug 2018 17:39:32 -0400
Subject: [PATCH] calculate internal slab fragmentation from slots

---
 calculate_waste.py | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/calculate_waste.py b/calculate_waste.py
index 7a87204..95a2223 100755
--- a/calculate_waste.py
+++ b/calculate_waste.py
@@ -1,5 +1,7 @@
 #!/usr/bin/env python3
 
+from sys import argv
+
 size_classes = [
     16, 32, 48, 64, 80, 96, 112, 128,
     160, 192, 224, 256,
@@ -11,6 +13,17 @@ size_classes = [
     10240, 12288, 14336, 16384
 ]
 
+size_class_slots = [
+    256, 128, 128, 64, 51, 42, 36, 64,
+    51, 64, 64, 64,
+    64, 64, 64, 64,
+    64, 64, 64, 64,
+    16, 16, 16, 16,
+    8, 8, 8, 8,
+    8, 8, 8, 8,
+    5, 6, 4, 4
+]
+
 print("size class", "worst case internal fragmentation", sep=", ")
 
 print(16, "100%", sep=", ")
@@ -24,6 +37,16 @@ for i in range(len(size_classes) - 1):
 def page_align(size):
     return (size + 4095) & ~4095
 
+print()
+print("size class", "slab slots", "worst case internal fragmentation for slabs", sep=", ")
+for size, slots in zip(size_classes, size_class_slots):
+    used = size * slots
+    real = page_align(used)
+    print(size, slots, str(100 - used / real * 100) + "%", sep=", ")
+
+if len(argv) < 2:
+    exit()
+
 max_bits = 256
 max_page_span = 16