chore: add screenshot, grammar/spelling

book/writing-programs/cycle-tracking.md

@@ -58,20 +58,24 @@ This will log the cycle count for `block name` and include it in the `ExecutionR
 
 ### Profiling a ZKVM program 
 
-Profiling a zkvm program is a good way to get an understanding of what is bottlenecking your program, note only one program may be profiled at a time.
+Profiling a zkvm program is a good way to get an understanding of what is bottlenecking your program. Note only one program may be profiled at a time.
 
-To profile a program, you have to setup a script to execute the program, 
-many examples can be found in the repo, such as this ['fibonacci'](https://github.com/succinctlabs/sp1/blob/12f212e386ae4c2da30cf6a61a7d87615d56bdac/examples/fibonacci/script/src/main.rs#L22) script.
+To profile a program, you have to setup a script to execute the program.
 
-Once you have your script it should contain the following code:
+Many examples can be found in the repo, such as this ['fibonacci'](https://github.com/succinctlabs/sp1/blob/12f212e386ae4c2da30cf6a61a7d87615d56bdac/examples/fibonacci/script/src/main.rs#L22) script.
+
+Once you have your script it should look like the following: 
 ```rs 
     // Execute the program using the `ProverClient.execute` method, without generating a proof.
     let (_, report) = client.execute(ELF, stdin.clone()).run().unwrap();
 ```
 
-The data captured by the profiler can be quite large, you can set the sample rate using the `TRACE_SAMPLE_RATE` env var.
-To enable profiling, set the `TRACE_FILE` env var to the path where you want the profile to be saved.
+As well you must enable the profiling feature on the SDK:
+```toml
+    sp1-sdk = { version = "3.0.0", features = ["profiling"] }
+```
 
+The `TRACE_FILE` env var tells the executor where to save the profile, and the `TRACE_SAMPLE_RATE` env var tells the executor how often to sample the program.
 A larger sample rate will give you a smaller profile, it is the number of instructions in between each sample.
 
 The full command to profile should look something like this
@@ -85,4 +89,5 @@ To view these profiles, we recommend [Samply](https://github.com/mstange/samply)
     samply load output.json
 ```
 
-Samply uses the firefox profiler to create a nice visualization for your programs execution.
+Samply uses the Firefox profiler to create a nice visualization of your programs execution.
+![An example screenshot of the Firefox Profiler](../profiling.png)

crates/core/executor/src/executor.rs

@@ -111,7 +111,9 @@ pub struct Executor<'a> {
     /// A buffer for stdout and stderr IO.
     pub io_buf: HashMap<u32, String>,
 
-    /// The ZKVM profiler.
+    /// The ZKVM program profiler.
+    ///
+    /// Keeps track of the number of cycles spent in each function.
     #[cfg(feature = "profiling")]
     pub profiler: Option<(Profiler, BufWriter<File>)>,
 
@@ -192,7 +194,7 @@ impl<'a> Executor<'a> {
         Self::with_context(program, opts, SP1Context::default())
     }
 
-    /// Crete a new runtime for the program, and setup the profiler if `TRACE_FILE` env var is set
+    /// Create a new runtime for the program, and setup the profiler if `TRACE_FILE` env var is set
     /// and the feature flag `profiling` is enabled.
     #[must_use]
     pub fn with_context_and_elf(

crates/core/executor/src/profiler.rs

@@ -14,8 +14,6 @@ pub enum ProfilerError {
     Serde(#[from] serde_json::Error),
 }
 
-/// The ZKVM Profiler.
-///
 /// During execution, the profiler always keeps track of the callstack
 /// and will occasionally save the stack according to the sample rate.
 pub struct Profiler {
@@ -51,8 +49,8 @@ impl Profiler {
         let mut function_ranges = Vec::new();
         let mut builder = ThreadBuilder::new(1, 0, std::time::Instant::now(), false, false);
 
-        // We need to extract all the functions from the elf file
-        // and thier corresponding PC ranges.
+        // We need to extract all the functions from the ELF file
+        // and their corresponding PC ranges.
         let mut main_idx = None;
         for sym in &elf.syms {
             // check if its a function
@@ -63,7 +61,7 @@ impl Profiler {
                 let start_address = sym.st_value;
                 let end_address = start_address + size - 4;
 
-                // Now that we have the name lets immediately intern it so we only need to copy
+                // Now that we have the name let's immediately intern it so we only need to copy
                 // around a usize
                 let demangled_name = demangled_name.to_string();
                 let string_idx = builder.intern_string(&demangled_name);
@@ -180,7 +178,7 @@ impl Profiler {
                 last_known_time,
                 sample.stack.into_iter(),
                 // We don't have a way to know the duration of each sample, so we just use 1us for
-                // all instructions
+                // all instructions.
                 std::time::Duration::from_micros(self.sample_rate),
             );