tests: basic benchmarking test framework (#12964)

This change adds a basic benchmarking test framework for Ollama which can
be used to determine the prefill, eval, load duration, and total duration
for running a given model or models.

cmd/bench/README.md

@@ -0,0 +1,114 @@
+Ollama Benchmark Tool
+---------------------
+
+A Go-based command-line tool for benchmarking Ollama models with configurable parameters and multiple output formats.
+
+## Features
+
+ * Benchmark multiple models in a single run
+ * Support for both text and image prompts
+ * Configurable generation parameters (temperature, max tokens, seed, etc.)
+ * Supports benchstat and CSV output formats
+ * Detailed performance metrics (prefill, generate, load, total durations)
+
+## Building from Source
+
+```
+go build -o ollama-bench bench.go
+./bench -model gpt-oss:20b -epochs 6 -format csv
+```
+
+Using Go Run (without building)
+
+```
+go run bench.go -model gpt-oss:20b -epochs 3
+```
+
+## Usage
+
+### Basic Example
+
+```
+./bench -model gemma3 -epochs 6
+```
+
+### Benchmark Multiple Models
+
+```
+./bench -model gemma3,gemma3n -epochs 6 -max-tokens 100 -p "Write me a short story" | tee gemma.bench
+benchstat -col /name gemma.bench
+```
+
+### With Image Prompt
+
+```
+./bench -model qwen3-vl -image photo.jpg -epochs 6 -max-tokens 100 -p "Describe this image"
+```
+
+### Advanced Example
+
+```
+./bench -model llama3 -epochs 10 -temperature 0.7 -max-tokens 500 -seed 42 -format csv -output results.csv
+```
+
+## Command Line Options
+
+| Option  	| Description | Default |
+| -model	| Comma-separated list of models to benchmark	| (required)		|
+| -epochs	| Number of iterations per model		| 1			|
+| -max-tokens	| Maximum tokens for model response		| 0 (unlimited)		|
+| -temperature	| Temperature parameter				| 0.0			|
+| -seed		| Random seed					| 0 (random)		|
+| -timeout	| Timeout in seconds				| 300			|
+| -p		| Prompt text					| "Write a long story."	|
+| -image	| Image file to include in prompt		| 			|
+| -k		| Keep-alive duration in seconds		| 0			|
+| -format	| Output format (benchstat, csv)		| benchstat		|
+| -output	| Output file for results			| "" (stdout)		|
+| -v		| Verbose mode					| false			|
+| -debug	| Show debug information			| false			|
+
+## Output Formats
+
+### Markdown Format
+
+The default markdown format is suitable for copying and pasting into a GitHub issue and will look like:
+```
+ Model | Step | Count | Duration | nsPerToken | tokensPerSec |
+|-------|------|-------|----------|------------|--------------|
+| gpt-oss:20b | prefill | 124 | 30.006458ms | 241987.56 | 4132.44 |
+| gpt-oss:20b | generate | 200 | 2.646843954s | 13234219.77 | 75.56 |
+| gpt-oss:20b | load | 1 | 121.674208ms | - | - |
+| gpt-oss:20b | total | 1 | 2.861047625s | - | - |
+```
+
+### Benchstat Format
+
+Compatible with Go's benchstat tool for statistical analysis:
+
+```
+BenchmarkModel/name=gpt-oss:20b/step=prefill 128 78125.00 ns/token 12800.00 token/sec
+BenchmarkModel/name=gpt-oss:20b/step=generate 512 19531.25 ns/token 51200.00 token/sec
+BenchmarkModel/name=gpt-oss:20b/step=load 1 1500000000 ns/request
+```
+
+### CSV Format
+
+Machine-readable comma-separated values:
+
+```
+NAME,STEP,COUNT,NS_PER_COUNT,TOKEN_PER_SEC
+gpt-oss:20b,prefill,128,78125.00,12800.00
+gpt-oss:20b,generate,512,19531.25,51200.00
+gpt-oss:20b,load,1,1500000000,0
+```
+
+## Metrics Explained
+
+The tool reports four types of metrics for each model:
+
+ * prefill: Time spent processing the prompt
+ * generate: Time spent generating the response
+ * load: Model loading time (one-time cost)
+ * total: Total request duration
+