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Tiny structural improvement of README. #199

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27 changes: 22 additions & 5 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -16,23 +16,38 @@ Inspired heavily by [gperftools](https://code.google.com/p/gperftools/), and wri
In your Gemfile add:

```ruby
gem 'stackprof'
gem "stackprof"
```

Then run `$ bundle install`. Alternatively you can run `$ gem install stackprof`.


### Run

in ruby:
The `StackProf.run` method accepts a block with your code to be profiled.

``` ruby
StackProf.run(mode: :cpu, out: 'tmp/stackprof-cpu-myapp.dump') do
StackProf.run(mode: :cpu, out: "tmp/stackprof-cpu-myapp.dump") do
#...
end
```

via rack:
The `:out` option specifies where the sample data is written to.

#### Mode

When profiling a less complex code chunk it might be more helpful to switch from `:cpu` mode to `:object`. This is
advisable when your `:cpu` run doesn't produce any samples.

``` ruby
StackProf.run(mode: :object, out: "tmp/stackprof-cpu-myapp.dump") do
#...
end
```
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I don't think this is accurate. You should only switch from :cpu to :object when you want to change from profiling time to profiling object allocations. If you run with :cpu doesn't produce any samples it means that your sampling frequency might not be high enough. Measuring :cpu vs :object are completely different things (some code could take lots of time but allocate no objects, some code could run fast but allocate many objects).


#### Rack

In a Rack application, `stackprof` provides a convenient middleware.

``` ruby
use StackProf::Middleware, enabled: true,
Expand All @@ -41,7 +56,9 @@ use StackProf::Middleware, enabled: true,
save_every: 5
```

reporting:
### Reporting

The file produced by the profiler can be visualized to a human-readable form by using the `stackprof` CLI command.

```
$ stackprof tmp/stackprof-cpu-*.dump --text --limit 1
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