add --total option. See https://github.com/brendangregg/FlameGraph/pu…

src/bin/flamegraph.rs

@@ -173,6 +173,10 @@ struct Opt {
     )]
     title: String,
 
+    /// Set total width to this many samples
+    #[structopt(long = "total", value_name = "UINT")]
+    total: Option<usize>,
+
     /// Width of image
     #[structopt(long = "width", value_name = "UINT")]
     width: Option<usize>,
@@ -210,6 +214,7 @@ impl<'a> Opt {
 
         // set style options
         options.subtitle = self.subtitle;
+        options.total_samples = self.total;
         options.image_width = self.width;
         options.frame_height = self.height;
         options.min_width = self.minwidth;
@@ -365,6 +370,7 @@ mod tests {
             colors: Palette::from_str("purple").unwrap(),
             search_color: color::SearchColor::from_str("#203040").unwrap(),
             title: "Test Title".to_string(),
+            total_samples: None,
             image_width: Some(100),
             frame_height: 500,
             min_width: 90.1,

src/flamegraph/mod.rs

@@ -142,6 +142,12 @@ pub struct Options<'a> {
     /// Defaults to None.
     pub subtitle: Option<String>,
 
+    /// # of samples to size the flame graph width to. This is useful for comparing flame graphs
+    /// with different amounts of samples so the contents are sized relative to each other.
+    ///
+    /// Defaults to None, which means it will be determined by the input being charted.
+    pub total_samples: Option<usize>,
+
     /// Width of the flame graph
     ///
     /// Defaults to None, which means the width will be "fluid".
@@ -255,6 +261,7 @@ impl<'a> Default for Options<'a> {
             count_name: defaults::COUNT_NAME.to_string(),
             name_type: defaults::NAME_TYPE.to_string(),
             factor: defaults::FACTOR,
+            total_samples: Default::default(),
             image_width: Default::default(),
             notes: Default::default(),
             subtitle: Default::default(),
@@ -408,8 +415,23 @@ where
         )));
     }
 
+    // set # of samples used for the full width if argument specified is greater than the amount from the input provided
+    let timemax = match opt.total_samples {
+        None => time,
+        Some(total) => {
+            if total < time {
+                warn!(
+                    "Specified --total {} is less than actual total {}, so ignored",
+                    total, time
+                );
+                time
+            } else {
+                total
+            }
+        }
+    };
+
     let image_width = opt.image_width.unwrap_or(DEFAULT_IMAGE_WIDTH) as f64;
-    let timemax = time;
     let widthpertime_pct = 100.0 / timemax as f64;
     let minwidth_time = opt.min_width / widthpertime_pct;