pss/docs/metrics.en.md

Metrics

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PSS automatically computes a set of metrics at the end (or during) the simulation. This document explains each metric, its formula, what it represents, and how to read it in the charts.

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Per-Process Metrics

These metrics are computed individually for each simulated process.

Metric	Formula	What it means
Arrival Time	arrivalTime	Tick at which the process first entered the Ready queue
First CPU Tick	startTick	Tick at which the process first used the CPU
Finish Time	finishTick	Tick at which the process completed its execution
Response Time	startTick − arrivalTime	How long the process waited before receiving the CPU for the first time
Turnaround Time	finishTick − arrivalTime	Total lifetime of the process (arrival → completion)
Waiting Time	turnaround − cpuTime − ioTime	Total time spent in the Ready queue (doing nothing useful)
CPU Time	Σ ticks in Running state	Total CPU actually consumed
I/O Time	Σ ticks in Waiting state	Total time waiting for I/O devices
CPU Utilization	cpuTime / turnaround × 100	Percentage of the turnaround time the process was actually using the CPU
Bound Type	see below	Classification of the process as CPU Bound, I/O Bound, or Balanced

Table visualization

In the Per Process tab, each row displays inline horizontal mini progress bars next to the numeric values. The bars are proportional to the largest value of the same metric among all processes, enabling immediate visual comparison:

Column	Bar color
Response Time	Amber
Turnaround Time	Blue
Waiting Time	Orange
CPU Time	Emerald
I/O Time	Cyan
CPU Utilization	Violet → Blue gradient

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Global Metrics

Computed over the complete set of processes in the simulation.

Metric	Formula
Avg Response Time	Average of all processes' response times
Avg Turnaround Time	Average of all turnaround times
Avg Waiting Time	Average of all waiting times
CPU Throughput	completed processes / total simulation time
CPU Utilization (global)	Σ Running ticks / total time × 100
Total Simulation Time	Tick of the last completion event

In the Global tab, each time card (Response, Turnaround, Waiting) displays a bar proportional to the total simulation time, indicating "how much of that total time the average process spends in that state". The CPU Utilization bar uses an amber → green gradient to indicate utilization health.

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CPU Bound vs. I/O Bound Classification

At the end of the simulation, each process is automatically classified based on the proportion of time spent on CPU and I/O:

cpuRatio = cpuTime / (cpuTime + ioTime)
ioRatio  = ioTime  / (cpuTime + ioTime)

cpuRatio ≥ 0.65  → CPU Bound
ioRatio  ≥ 0.65  → I/O Bound
otherwise        → Balanced

• CPU Bound: the process spends most of its time using the processor.
• I/O Bound: the process spends most of its time waiting for I/O devices.
• Balanced: the process uses CPU and I/O in a balanced way.

In the process list: estimate computed from the declared bursts (before simulation).
In the metrics table: classification computed from the actual recorded times.

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Charts ("Chart" tab)

Comparative Profile (Radar Chart)

Displayed when there are 2 or more processes. Each axis represents a time dimension, normalized from 0–100% relative to the largest value in that dimension among all processes:

Axis	Meaning
Turnaround	Relative total lifetime
Response	Relative time to first CPU
Waiting	Relative time in the Ready queue
CPU Time	Relative CPU usage
I/O Time	Relative I/O usage

Each process is drawn as a colored polygon (the color configured for the process). Wider polygons indicate processes with larger times in the corresponding dimensions. The radar chart is ideal for identifying profile differences between processes (for example, a CPU Bound process will have a much larger CPU Time axis than I/O Time).

Per-Process Breakdown (Stacked Bar Chart)

Always displayed. Each bar represents a process, with stacked segments:

• Amber: Waiting Time
• Green: CPU Time
• Cyan: I/O Time

The total height of each bar equals the Turnaround Time of the process.

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Thread Metrics

When a process has threads, PSS computes individual metrics for each thread. These metrics are displayed in the Threads tab of the metrics panel (visible only when there are processes with threads).

Per-Thread Metrics

Metric	Formula	What it means
Arrival Time	arrivalTick	Tick at which the thread first entered the Ready queue
Start	startTick	Tick at which the thread first used the CPU
Finish	finishTick	Tick at which the thread completed all of its bursts
Response Time	startTick − arrivalTick	How long the thread waited before receiving the CPU for the first time
Turnaround Time	finishTick − arrivalTick	Total lifetime of the thread (arrival → completion)
Waiting Time	turnaround − cpuTime − ioTime	Time in the Ready queue without doing anything useful
CPU Time	Σ ticks in Running state	Total CPU consumed by the thread
I/O Time	Σ ticks in Waiting state	Total time waiting for I/O

Thread Models and their impact on metrics

The thread model directly affects the recorded times:

Model	Impact on Waiting Time
MANY_TO_ONE	Waiting Time tends to be high: any thread's I/O blocks the entire process, forcing other threads to wait
ONE_TO_ONE	Lower Waiting Time: threads block independently; while one does I/O, the others remain in the Ready queue
MANY_TO_MANY	Intermediate Waiting Time: threads that exceed the kernel slots enter KernelWait (shown with reduced opacity in the Gantt chart)

Visualization

The thread table displays inline horizontal mini progress bars in the Response, Turnaround, Waiting, CPU, and I/O columns, normalized by the largest value in each column across all threads — just like the process metrics table.

Each thread has a color derived from the parent process color (40° HSL hue shift per thread), shown as a colored dot in the table and as a sub-row in the Gantt chart.

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Example

Consider three processes with the following bursts:

Process	Bursts	cpuTime	ioTime	cpuRatio	Classification
P1	CPU:8, IO:1, CPU:1	9	1	90%	CPU Bound
P2	CPU:1, IO:8, CPU:1	2	8	20%	I/O Bound
P3	CPU:4, IO:2, CPU:4	8	2	80%	CPU Bound