Add cpu doc

Author: MathieuCesbron

README.md

@@ -11,10 +11,10 @@ Kondense is an automated resource sizing tool. It runs as a sidecar in kubernete
 ## Background
 
 ### Memory
-Kondense uses memory pressure to apply just the right amount of memory on a container to page out the unused memory while not getting out-of-memory killed.
+Kondense uses memory pressure to apply just the right amount of memory on a container to page out the unused memory while not getting out-of-memory killed.</br>[How is memory calculated ?](./doc/memory.md)
 
 ### CPU
-Kondense resizes CPU based on CPU usage, default to 80%.
+Kondense resizes CPU based on CPU usage, default to 80%.</br>[How is CPU calculated ?](./doc/cpu.md)
 
 ## Requirements
 

doc/cpu.md

@@ -0,0 +1,25 @@
+# How is container CPU calculated ?
+Kondense resize each container CPU every second with the following steps.
+
+## 1. Calculate average CPU usage of the container.
+Kondense calculate the average CPU usage over the last `INTERVAL` seconds. By default, `INTERVAL` is 10 seconds.
+
+### 2. Calculate new CPU
+To calculate the new container CPU, we need the `TARGET_AVG`. By default, `TARGET_AVG` is 0.8 so 80%.
+
+```
+new_cpu = average_cpu / TARGET_AVG
+```
+
+### 2.1 If `new_cpu` is smaller than current container cpu limit
+
+If `new_cpu` is smaller than the current container limit, we just patch container CPU limit with this `new_cpu`.
+
+### 2.2 If `new_cpu` is bigger than current container cpu limit
+
+If this `new_cpu` is higher than the current CPU container limit, we exponentially increase `new_cpu` with this formula:
+```
+new_cpu = new_cpu + (new_cpu * coeff)²
+```
+The bigger the `coeff`, the stronger Kondense will increase the CPU.
+We patch the container CPU limit with this `new_cpu`.

doc/memory.md

@@ -0,0 +1,2 @@
+# How is memory calculated ?
+will come soon